[ddebernardy]

Not the OP, and I haven't used PG regularly for a few years, but back then I vaguely recollect the query optimizer not behaving consistently based on whether you had a full column with a GIN (or GIST) index and a (potentially partial) index on an expression for some reason. In a nutshell it preferred using the full column with an index rather than the expression index.

Even more importantly in some circumstances, having the full column allows the optimizer to pick another index when it's totally relevant, and filter the relevant rows without needing to recompute the TSV one by one for the subset.