I think the short test is a better predictor of your FTP than the ramp test. I’ve heard that the ramp test can over estimate the number, but it is also good to use both or all 3 tests to verify the numbers you are getting.
Shayne from GC Coaching has commented on this in their podcast “Never Going Pro” - a ramp test is a great way to judge what your max aerobic power is or VO2 max things like that. But a true FTP test should be a lot longer like 20 to 30 minutes, ideally. And then if it’s a 20 minute tests, you should ideally do some kind of burn out effort, like I think Zwift uses the three or five minute 115% effort before because you’re trying to decrease your anaerobic contribution to the power produced. That’s why people have a ramp test and they have a super high FTP because it’s being over inflated.