[License]Is Bison exception only valid on Bison 2.2?

Dear all,
Bison is a useful tool!
I have one question about the license of generated files by Bison.

It shows GPL exception with bison as following.  Is the exception only
valid on Bison 2.2? or still valid on later versions?
"This special exception was added by the Free Software Foundation in
version 2.2 of Bison."

Is it possible to modify bison utility to make that statement more
clear(2.2 and after) ?
thank you very much

best regards,
Kuohong