do I just force like this?

Probably better to replace the

$PDK

in the .mag file. I don't know who put it there. It's not valid syntax for a .mag file so possibly it is intended to be run through a filter and replaced, or maybe somebody didn't know what they are doing. But the wrapper file should be valid with either sky130A or sky130B, since it's just a wrapper, so you can just do

load user_project_wrapper -force

after starting magic with the appropriate PDK and it should read in fine.