Why does it take so long for the iPhone to recognize when space has been freed up for photos?

Question

The short story:
I try to take a photo using the built in camera app. I get the dreaded 'no enough storage' message.
I then delete a bunch of photos, podcasts, etc. effectively freeing up plenty of space to take a photo.
Nope - iPhone Camera still things there is no space available.
After some unknown time delay - 10 minutes or more, in many cases, it will FINALLY let me take a photo.
The longer and more detailed story:
I know EVERYONE gets this message at one time or another and I know how to resolve it: "Cannot Take Photo - There is not enough available storage to take a photo. You can manage your storage in Settings."
Fine. I understand that. I'm out of space on my phone (not iCloud, as some users seem to confuse). It's a no brainer - you don't have enough space on your phone to take a new picture. Again - fine, I get that.
What I DON'T get, and what drives me absolutely NUTS, is that I will then go through my photos and delete a dozen or so that I don't really want, easily freeing up a good 20Mb or more, then when I try to take a photo again, I STILL GET THE out of space MESSAGE! Baloney. I am NO LONGER out of space. iPhone, you incredibly well designed and intelligent piece of hardware, why, for the love of all that is good, can't you figure out that I know have 20Mb free?
So, then I'll jump over to Podcasts, which I love, but take up lots of room on my phone. I'll delete a few of the large ones I've already listened to, easily freeing up a few HUNDRED MEGABYTES. We should be good to go, right? WRONG. The iPhone genius still tells me I don't even have enough space to eek out one lousy photo.
If I let my phone sit there long enough -- 10 minutes, 30 minutes, a few hours -- I haven't determined when the magic happens -- eventually the iPhone realizes that 'Hey, the user just deleted a bunch of junk and, wow, I'll be a son of a gun -- there IS enough space now to take a photo. iPhone -- happy!'
Thanks for nothing, iPhone. By this time, my daughter has stopped doing that amazing cute thing that I wanted to capture forever and quite possibly spawn the next generation of 'Charlie Bit Me' parodies. I freed up 500 Mb of prime photo snapping space 20 minutes ago. Thanks for finally realizing it. I realize you can only do like 170 quadrillion calculations a millisecond. I realize these things take time.
Can one of you iPhone engineers please, for goodness sake, please explain to me why this INFURIATING and seemingly unnecessary delay exists? I am no Windows fan boy but I can sure tell you that when I'm running low on hard drive space on my laptop and then delete 1GB of files, that 1GB INSTANTLY becomes available to me. I don't have to wait some interminable timeframe until it magically is usable.
One last thing that is puzzling -- so the native iPhone camera will refuse to let me take a photo because it things we're out of space (when we're not) but any third party photo app, like Camera+ or Camera Awesome, will happily snap pictures all day long. In fact, once I've taken them using one of these apps, I can then SAVE THEM TO THE CAMERA ROLL!
By the way -- when I started this well thought out rant, my iPhone said it was out of storage, and now, five minutes later -- you guessed it -- still out of storage, despite the fact that I deleted 10 photos and 4 podcasts.
So. Incredibly. Infuriating.
For you iOS 7 users, please let me know if this issue has been resolved at all with iOS 7. I've held off upgrading because iOS 7 messed up a bunch of things with the camera, at least on my wife's iPhone 5. Focus no longer works reliably -- touch to focus and touch to expose no longer work well -- the quality of photos took a big hit. I won't update until these issues have been resolved.

Answer 1

Thanks @pdroth. I did a quick Google search of DB indexing. I'm not sure I found exactly what you were referring to but I see where you're going with it. I can understand that indexing my database of stored photos can be time consuming. It's frustrating that the space can't be recognized as being free more quickly.
I notice that some items I delete seem to free up the space much more quickly. Removing an app entirely or deleting from my Music generally shows up as available space in Usage pretty quickly.
Deleting a photo or video from the Camera Roll will take MUCH longer, so I guess that has something to do with the indexing process you are referring to.
I'd like to point out that when I run out of space on an SD card on any budget point and click digital camera that I can quickly delete a picture or two and INSTANTLY be able to take a couple of new photos in their place. I guess I just have that same expectation for the $500+ engineering marvel I have in my hand right now.
Thanks for chiming in.