Partitioned tables and locks

Is it expected that a lock on a partitioned table will take out 2 locks per
child regardless of the number of children which are excluded at plan time?

For example I can select count(*) from a table with 3500 partitions in
transaction, and see 7000 AccessShareLocks show up till I finish the
transaction.

Bonus question - sometimes if I query pg_locks fast enough I can see ~30K
locks - how could this possibly be the case. This is on an otherwise idle
system.

Cheers,
James

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