postgresql logical replication -- subscriber size discrepancy
This is to be expected and no problem.

When logical replication starts, it copied the existing data from the source tables. The data in the target tables will then be densely packed and consume less space.

As replication proceeds, the target tables get modified and &ldquo;dead tuples&rdquo; will accumulate and be removed by autovacuum. The tables will become slightly &ldquo;bloated&rdquo; over time, which is normal and healthy.

Since you don't plan to use logical replication for a long time, the replica will probably never grow as big as the original.