With those ESCs, it is not surprising to see them turn on soo high.
Try using some other testing source, like arduino (with pulse value display). like this would work https://robu.in/product/digital-servo-tester-esc-consistency-tester/?gad_source=1&gad_campaignid=20381096599&gbraid=0AAAAADvLFWcpiWDqxIH14rVfS04qJMtI0&gclid=CjwKCAiAnoXNBhAZEiwAnItcGwVoK2EbqptA8_qUHo--9LpKdhzxE_ubHSR-PBIDBsBNoODhZZqEqhoCMLEQAvD_BwE
if it turns on only at 1200us, then its issue of esc
You should also consider replacing these motors, they have collet prop adapter, which give a lot of vibration - not good for flight.
Also see this list - Hardware To Avoid When Building Your First Multirotor