Yes, that's how you get Snow Leopard installed on some Macs. Just a result of Apple not providing full installers for later versions of some OS X systems. Same for full install of Leopard, which was only released to version 10.5.6, Tiger to verston 10.4.6, and the earlier Panther to version 10.3.5
Apple finally fixed Lion to the latest version 10.7.5, which was related to Lion being the first version to support the Recovery/ Internet Recovery boot, where the latest version installer might always be available through your internet connection. Made a big difference in convenience for how the system could be installed. Simply not as convenient on systems before Lion.
There are some users who discovered how to modify the original 10.6.3 installer to add those parts of the install to make a later version (and overcome the need to have another, older Mac to assist in a reinstall of Snow Leopard.
Then, there is also the OTHER method to connect the two Macs with a Firewire cable, then boot your target MBPro to target boot mode, then boot your older Mac to your Snow Leopard installer, then choose the drive in your newer Mac as the destination to install Snow Leopard. After the install is complete, you can boot to the normal drive on the older Mac, then update the newer Mac to 10.6.8 with the normal combo updater to finish the install. And, you shouldn't need to move drives between the two Macs. All you need is a Firewire cable