So I think what you're saying is, if the torque converter locks up in 3rd gear, it might kinda sound like a shift to 4th. If the torque converter is locked, tapping the brake signals the car to unlock it, and if you're still holding the accelerator steady, RPM should jump up.

Took a 2-3 mile loop and tried that, several times. RPM held steady when I tapped the brake.