also, i should just point out that this compact format incurs more processing cost... in a database, for example, you still have to have all the truncated pubkey in the indexes still, but in the database you don't need to verify it, it is only on the submission process that this all has to be derived

plus, having the pubkey in the part that generates the hash acts as a namespace that reduces the chances of a two messages from different keys ever colliding, so, probably there is no logic to switching to this type of compact signature