discrepancy in tz handling in time comparison and equality functions

hello

in the xacml 2.0 spec definitions for
"urn:oasis:names:tc:xacml:1.0:function:time-greater-than" and other
comparison functions there's a note:

Note: it is illegal to compare a time that includes a time-zone value with one
4363 that does not. In such cases, the time-in-range function should be used.

while it's not in the difintion of
"urn:oasis:names:tc:xacml:1.0:function:time-equal" function.

I understand that it has something to do with the partial ordering of
time values, when only one of them has tz set. However, I don't
understand why then equal and comparison functions are treated
differently. It seems that for "equal" function, it's not illegal to
compare values when only one of them has tz, the other one will be set
to a "default" time zone. is that true?

thanks
argyn