As Taz hinted, GM's TIS2WEB does not have any sanity checks on what you are trying to do, if you manage to get it to flash say a 2007 E67 OS in to a 2010 E67 ECM then it will corrupt/brick it 100% guaranteed to happen, that is why we won't remove those restrictions and this applies to any controller (TCM's included). Mind you they are getting better with the late model stuff where they do check some part numbers before allowing the flash.
Taz is also correct in that if you have a 2006 E67 from a Pontiac G6 GTP 3.9L and you are using it on a 2006 Northstar V8 then yes you must use TIS2WEB so all 8 segments are flashed. The secondary CPU (the last two segments) are not readable therefore only TIS has the means to flash it because all the files are stored at the GM HQ servers. And to be honest the thought of flashing the very thing that oversees correct throttle operation is not something I'd be happy with.