It seems that changing this parameter worked for me.
Setting it to zero means that there wont be any parallel workers for one query right ?
Is it something familiar this problem with the gatherers ?
Your example would not be using parallel workers anyway, regardless of the setting of max_parallel_workers_per_gather, so I don't see how changing this could have worked for you. Unless you mean it worked in your full test, rather than in your test case. I doubt your test case benchmarking was very reliable to start with, you only show a single execution and didn't indicate you had more unshown ones.
If I do more credible benchmarking, I do get a performance regression but it closer is to 16% than to 3 fold. And it doesn't depend on the setting of max_parallel_workers_per_gather. I doubt a regression of this size is even worth investigating.
