That could be it... Trump is trying to signal that this shouldn’t be considered a huge deal.
The problem is, I think it is a huge deal in terms of its subjective impact.
I’d say let Hillary try to stump for this. It will prove poison to her candidacy. In the meantime Trump can be all 10th Amendment about it, and will smell like a rose from a constitutional point of view. A president who sees a bigger role for the states is going to be welcome to constitutional aficionados.
Trump has to make clear that his SCOTUS judges will leave it to the states as they should, while Hillary’s judges would mandate trannies in the bathroom of their choosing nationwide under penalty by the federal bureau of transgender rights.