Clone teensy’s from hong kong have been found to provide 5v even with tracks cut/bridged and a regulator attached, or even no regulator attached when powered by ps3.
it is caused by the way the boards tracks are wired up. it will take its power from the usb anyway and when the teensy is connected to the ps3 5v is still delivered from usb at the same time as 3.3v from the ps3.
The solution to this problem is to cut the +5v wire in the usb lead that’s used while downgrading. Make sure you don’t cut the ground wire as this is needed.
hope this saves someone some time when using them. besides that they work just fine.