STCompiler, at least, uses the #import: message on classes to implement that pragma. Unfortunately the empty version in Builtins.st shadowed the proper definition in ClassDesc.st:

Object: nil error: did not understand #at:ifAbsent:
...
STInST.STCompiler>>acceptMessageNode:

where nil is supposed to be VMSpecialMethods. Fixed in smalltalk--backstage--2.2--patch-68 by promoting said empty version to ClassDescription.

Like:

../gst-tool gst-doc -I ../gst.im --kernel-dir ../../../ide/smalltalk/kernel -p BloxTK -o ../../../ide/smalltalk/doc/blox.texi BLOX.* || \
          rm -f ../../../ide/smalltalk/doc/blox.texi
gst-doc: package not found
test -f ../../../ide/smalltalk/doc/blox.texi && touch ../../../ide/smalltalk/doc/gst-libs.texi 
make[2]: *** [../../../ide/smalltalk/doc/blox.texi] Error 1