Considering 'M' a STM32Duino board as master.
Considering 'S' a STM32Duino board as slave.

1/ Having in setup() for both M and S function TwoWire::setClock(100000)
=> receiveEvent and requestEvent never called in S

2/ Having in setup() for M only function TwoWire::setClock(100000)
=> receiveEvent and requestEvent are called in S as expected.

Maybe the right way is to have this function working for masters only??? I don't know as I am not an i2c expert.