create index insist on 2 workers only

Hello everybody,

We 're rebuilding a big table which has set parallel_workers = 6
system has
max_parallel_maintenance_workers | 6 |
/var/lib/pgsql/11/data/postgresql.sumup.conf
max_parallel_workers | 16 |
/var/lib/pgsql/11/data/postgresql.sumup.conf
max_parallel_workers_per_gather | 4 |
/var/lib/pgsql/11/data/postgresql.sumup.conf

Also session level on index restore there is
set max_parallel_maintenance_workers = 6;

Still we get only 2 parallel processes in a free of any other load system.
It is postgres 11.7

Where to look at ?

Thank You very much

Rado