The IEEPA one works where it can last as long as the "emergency," which Congress can vote to end. The "days don't count as days" game just lets the House have an easier time of not bringing it up for a vote.

This other authority is different: it's limited within the law to 150 days and then has to be extended by Congress. So the same kind of strategy of just avoiding a vote doesn't work here. They could monkey with the deadline, but can't do so any more easily than just actually extending the tariff for real. Of course just like today you can have Trump jump to some new authority on day 151 instead.