Rant Alert: zFTP

Zwift is a great cycling app - theres so much to like. But.....zFTP must be one of the silliest inventions I've seen. If you do an ftp test (20min+ if you want any accuracy) then you have the best estimate amd don't need it. If you don't do an ftp test, then you have zftp....which for me is a full 35W less than what I'm confident ny ftp is and 30W lower than intervals eftp. This is a huge gap, and I'm not doing anything silly. I've got maximal efforts up to 12 minutes and have done 1x60 sweet spot at zftp. I've also done my own estimate of ftp for 55 mins in normalised power, but staying in aerobic power ranges (sub vo2 max) I don't believe I'm doing anything odd or have a particularly strange power curve.

If i naively used zftp for training it would be way too light below ftp.

So.....should zftp just be consigned to the dustbin as it is worse than an uniformed guess...