Is this sop not part of the 21.0.440 release?

Couldn't find it either. That's so weird... it's in the document of 21.0.440 local installation.

Attribute Fill SOP now has Extrapolate mode, which does Parallel transport with the same options (Parallel Transport and Radial Fields) as described on that Parallel Transport SOP docs page

so my assumption is that this node was consolidated into Attribute Fill before the release