None of the above is totally correct.
The mid 2010 MBP was supplied with a grey disk with a newer build number than the retail 10.6.3 disk. That means it will not install from a 10.6.3 retail disk onto a 2010 MBP. Fact ! I have a mid 2010 MBP and a retail 10.6.3 disk, and have tried several times to do this. Trust me - it does not work.
Omaticnyc is right though that the MBP will boot from the retail disk - but the install will not complete - it fails after 10 minutes or so with no error message, and the machine then hangs. The same thing happens if you load the disk and choose it in Startup disk then restart. The odd thing about this latter method is that usually Startup disk flags up when a disk is unsuitable for a particular computer - in this case it doesn't.
This leaves post April 2010 MBP owners dependent on keeping hold of a working grey disk for their machine if they want to stick with Snow Leopard AND stay within their licence terms. And means buyers of secondhand MBPs MUST get the original disks. Or upgrade to a post Snow Leopard OS.
There is though a way round all this - unfortunately it probably isn't within the licence Ts & Cs...
When Leopard came out, it required an 867 MHz processor to boot/install. There were several workarounds to this, one of which was to install Leopard onto a drive in a compatible computer, then switch the drive (or clone it) to a slower one. And the same trick works to boot/install from the 10.6.3 retail disk onto a post April 2010 MBP. I've done it using a Mac Mini to install 10.6.3 then the 10.6.8 combo upgrade, and the only downside I can see is that the MBP then shows up as a Mac Mini in System Profiler.
The real shame (and maybe even stupidity on Apple's part) is that for 15 months no retail OS disk was/is available for any MBP and perhaps for any other computer built in this period. Makes you wonder what the purpose of retail disks is...either they're universal install media...or they're a means of generating extra revenue. And if it's the former, then a retail disk should be made available at the point of upgrading from one OS to the next - indeed if Apple could include Drop in DVDs at upgrade time, then a complimentary fully upgraded disk could have been included too.
Better yet someone could/should devise a method of streamlining Mac OS disks...