The Talmud says makes says that kissing and hugging an idol would be לאו שבכללות an prohibition that includes lots of things and so can't get lashes.
[That was not the original statement of Rav Avin bar Kahana. At first he had said one does lashes for it. Frankly this makes a lot more sense to me. But I can't go into that right now.]
At any rate Tosphot this is not like on Passover one can't eat Passover sacrifice raw or boiled in which the Prohibition for each  is stated openly. This is fine except that tosphot says the lashes are for "only roasted" "כי אם צלי אש". The problem is raw is one of the 613 commandments. And so is boiled. So why would they not get lashes because of themselves? Why only because of "only roasted" "כי אם צלי אש". I am not asking this as a question as much as just something that means we have to study Pesachim 41 where this comes up. [Lashes are the punishment for a prohibition in the Torah when the punishment is not stated explicitly. It can only be given if there were two witnesses that gave warning beforehand. It is a version of Miranda rights. There is never any punishment unless a warning is issued beforehand that is accepted by the perpetrator.]]

The end of this Tosphot however says something that is at face value really difficult. that don't serve idols is not specific enough while don't do work on the festival is specific.
to me it seems that it is impossible to know what Tosphot could mean by this without first spending time on pesachim pg 41. What could be the difference? I thought perhaps the festival has 39 kinds of work while honoring an idol could have an infinite range of things. But still why is it different? Don't do any work and don't do anything that honors an idol seem to be specific in the same way.