Validation inconsistency between TopStyle 4 und CSE HTML 10?

[wjs]

In css I defined by mistake "h1a". It should be a class-definition; but in TopStyle it was listed as element (I forgot the dot like ".h1a", I know).

Validation via TopStyle: no message, everything seems to be ok.
Validation via CSE HTML Validator: report message "The "h1a" is not a recognized element in this selector. Is it misspelled?"

Thank you CSE HTML Validator to identify that error (as it is one as far as I think); but why was this error not found by TopStyle (v4.0.0.84)?
Any explanation? Did I something wrong? Is it a bug?

Kind regards,
wjs