Frankly it's about as much a real sequel as the Melendez/Mendelson-produced "Frosty Returns" was. From a purist point of view, the only true blue sequels are the ones Rankin/Bass produced themselves (most of which, incidentally, are owned by Warner Bros. instead of Dreamworks, which was part of the reason these non-RB sequels were produced in the first place).
Some might argue but I actually like the Frosty sequels. I enjoyed them as a kid and still enjoy them to this day. While they might seem off putting given that they aren't made by Rankin Bass but I still love them as the storylines for both are just the way they're supposed to be with a ton of comic relief added in
I completely forgot about this monstrosity from 2001. They tried doing a Rudolph sequel and everything went horribly wrong. I remember watching it maybe once or twice as a child and hated everything about it