This has been the case since 3039u. All of the 3145 and xtro series were done in the same way. They haven’t even bothered to post a majority of the RS products after the migration to the new site. The ones that have appeared are for the most part directly related to TRO Succession Wars so it’s far from accidental. Though SSW and MML aren’t openly advertised, they aren’t discouraged either and I can understand why most people would opt for free in one place vs a couple hundred bucks across several files.
Amusingly, someone could have done one sheet a week as a side project and we still would have had RS: Prototypes years ago.
Maybe they’ve been sitting on a format change that we’ll see in the new box sets. Or maybe it’s just not worth the effort.