Bufferbloat worse with Flow Control enabled

Testing bufferbloat via: https://www.waveform.com/tools/bufferbloat?test-id=50c36e54-85e6-4b16-bdcc-afc13758983c

If I have Flow Control off, I'm seeing +8ms on download and +37-42ms on upload.

If I have Flow Control on, I'm seeing +8ms on download and +64-69ms on upload.

Wasn't Flow Control supposed to make this better not worse? I have a UCG Fiber running from my NTD & PC both over RJ45 with 3m cables. No other switches, no WiFi or anything else in the mix, and no other network activity during the test. Why is it so bad, and can I make it better somehow?

My UCG Fiber is only running UniFi network nothing else installed, no UniFi access/protect etc
And firewall features like intrusion detection, encrypted dns etc are all off. One VLAN, no policies, no DNS.. whats slowing it down? My network is 750/50 too, it shouldn't be bottle-necked by any hardware here.