Time constant vs Length of Pulse in RC circuit
That's right.
If the RC circuit has time constant of 100us, it has no chance to react to the 1us pulse, so it will pass on right through.
If on the other hand you needed to pass a 100us pulse with a RC circuit having also 100us time constant, the 100us pulse would have enough time charge up the RC circuit, so the waveform would have droop.
Same thing can be explained in frequency domain as well. If you have an RC high pass filter with 1 kHz cutoff frequency, it can pass 10kHz sine wave almost at the same amplitude as it comes in, but a 1 kHz sine wave would have attenuated by 3dB, because the signal is slow enough to charge the RC.