maintenance_work_mem impact?

I have a table approx. 20GB.

I have a create unique index statement.

CREATE UNIQUE INDEX testindex_v1 ON testtable1 (test_index); 

My observations:

maintenance_work_mem = 2G

max_parallel_workers = '16'

The create index completes in 20 minutes.

When I change this:

maintenance_work_mem = 16G

max_parallel_workers = '16'

It completes in 9 minutes. So I can see that I can gain performance by changing this number.

Thanks,
Ad