Yes that’s definitely the noise gate at work. And the more noise floor you have, the more you hear it. When I turn the boost on I definitely get more of a sizzling sound at the end. The interference I talked about earlier can also add into that.
There have been other threads on here about the different noise gates. Some people say they have analog pedals that do a better job.
Some people say the problem is the noise gate built into the input block and that they are happier with a “simple gate” block (which just abruptly cuts volume at a certain threshold or the newer “adaptive gate (S/C)” in the end of the chain but with sidechain set to input 1.
Personally I have never seen a device do this perfectly. You always have to compromise at some point.
Here is a recent thread about the topic:
https://unity.neuraldsp.com/t/noise-gate-on-input-block-not-working-correctly/12686