Those instructions are BS. Flash does not work on 2.1. There are several devices, such as the Galaxy S, that run Flash Lite however (it came on my Vibrant, for example). Someone with Flash Lite tried that and thought they had real Flash when really they just had Lite, and it spread for a while before being debunked. Just read the comments on that post.
Edit: According to Lie Ryan's comment below, full flash is compiled for ARMv7 chips, and so won't work on other processors even with 2.2.
Edit 2: Adobe now has a list of devices that run Flash: http://www.adobe.com/flashplatform/certified_devices/