That puppet is complex.
Puppets are an on-set effect during production. Post-production is after filming. Unless you're talking about the need to digitally erase the puppeteers and rods from all the shots, but that's been a routine process for decades. (I think the earliest use of digital rod removal may have been in Back to the Future Part 2 with the hoverboards.)
It's more likely the CG animation that would take a long time in post, and it's good if Disney is giving the artists enough time to do it right and not be worked to the bone.