I don’t think MS classes on a HS transcript is common here in CA, because the UC application and CSU application instruct kids to look at their MS transcript to find and enter eligible 7-8 grade classes (only Algebra, Geometry, and LOTE count in this case, not English or any other “high school level” classes, and the grades are not used).
But I think this probably varies a lot by state, and even within a state, may vary by high school. Here’s a thread where people talked about their HS policies about middle school courses and there seemed to be a ton of variation. Should high school level courses taken before high school count as credit on a transcript for college purposes