Yes, it makes sense. The piston is rendered by the other panel which can be covered by a cover.
Whether this is now a real bug I would like to put to one side.
It is also rather unimportant.

Nice edge case! ;) Not sure if this is worth fixing as it would either require changing the way pistons are rendered or having an exception for the non-rendering of a covered block which would introduce overhead that the cover is supposed to eliminate.