Not solely that way, no. The Constitution gives him other responsibilities:
Article I: "Every bill which shall have passed the House of Representatives and the Senate, shall, before it become a law, be presented to the President of the United States; if he approve he shall sign it, but if not he shall return it, with his objections to that House in which it shall have originated"
The President is explicitly prohibited from signing a bill of which he does not approve.
So, you are of the opinion that he signed it in expectation of it being kneecapped in the SCOTUS?
He signed a clearly unConstitutional (unConstitutional by your line of reasoning and mine) bill, yet he did not abrogate his Constitutional duty?
Let me repeat that.
He signed a clearly unConstitutional (unConstitutional by your line of reasoning and mine) bill, yet he did not abrogate his Constitutional duty?
I don't think you understand what duty means. Or honor for that matter.
EBUCK