This is just not true.
98-2001 black box and 0411 DO revert to full line pressure on the stock OS's if you don't change the settings like is described in my previous posts' linked thread on the HP tuners forum. It is not because the data isn't there for it to function, but because the OS is set up to do that when the MAF is failed. There are options in the OS to turn that off. A 2002 0411 OS will not default to full line pressure if the MAF is failed properly. There ARE custom SD OS's, but those are usually only to allow the 2 and 3 bar MAP sensors so that you can run boost. It is standard to fail the MAF sensor in the OS to revert the system to SD so that you can dial in the VE tables. Most people just let it go to full line pressure while doing this, since it doesn't really hurt anything. It just makes the shifting much harsher at low throttle conditions. I'm running an '02 OS, so I don't have this issue at all.
If you fail the MAF in the tune and then just hook up a line pressure gauge to the trans, you can tune the normal and abuse mode tables to set them properly based on what the PCM thinks the engine is doing.