Should it use it ? It occured to me to ask when reading Bruce's release notes, which say: | [MERGE] is similar to INSERT ... ON CONFLICT but more batch-oriented.
Currently, INSERT *never* uses bistate - even INSERT SELECT. INSERTing 10k tuples will dirty 10k buffers - not limited to the size of a strategy/ring buffer. Currently, MERGE will do the same. I had a patch for INSERT last year. https://commitfest.postgresql.org/35/2553/
