My opinion...
Mag blocks are fine if they dont allow the magazine to be readily converted to use more than 10 rounds. Frequently this is accomplished by epoxying the block in such that you cant open the magazine or otherwise make changes.
The entire 10rd mag thing whether factory or post factory pinned is a crap shoot. Lots of factory 10 rounders have one additional manufacturing step where they dimple the mag on both sides. You can remove the dimple with a drill in 3 seconds without impacting the integrity the magazine and welcome to full capacity. Some factory mags now are cut short and have a large plastic base so no way to ever convert (ok, weld on more metal).
Mags that have a base plate inside the mag with a cylinder that goes down into the actual base plate to hold it all together can be replaced with an internal base that has length to limit to 10. You cant just remove the new base because the mag falls apart. If you can get a new flat base, you can get the mag back to full capacity. That scenario requires new parts, so arguably ok (unless some DA hates you)
So pinned? factory? depends. Scar 10rds factory are not going to be modifiable by any definition of easy. They are not cheap, but readily available. Epoxied mag blocks done by your FFL are likely just as good in terms of permanent.