We really don't know anything yet, because nothing about the "system" is complete. From what I gather, only SFREP has a functional software, including a third party inspection app and a report software. Total and ACI are not even close to functional. Some of the new kids are full of promise, but don't have completed software yet (completed to mean both a mobile app and desktop report generator). Nor is the delivery system ready. Reports I have seen suggest there have been about 100 reports to the GSEs, all manually entered. The lenders' systems are reportedly way behind. Of course, insiders will tell you that none of these facts are accurate, but they will not provide any, so you rely on what you get!
I think appraisers' reactions are (quite) a bit overblown, but the unknowns are the problem. I haven't wasted time studying the minutia yet, but if AMCs, lenders, and the GSEs want to quibble about every little thing that doesn't make any difference to an appraiser, or their task, then they can grind the whole system into the ground. I suspect that is why some fields are "optional"...until the data flow begins functioning and steadying out. Then, the scope of work will be ramped up over the next months or years. And on a whim, they can revise the forms to add more.