The party in the House always threatens to not raise the debt ceiling if the POTUS is of a different party. It has been like this for decades.
It didn't really happen as much over the last 4 years.
As they say, the deficit hawk is a seasonal bird.
I think if you actually look at the history of this, you'll find that it's almost always the Republicans who threaten not to raise the debt ceiling.
Certainly, all the notable debt ceiling crises listed here[0] were instigated by Republican Congresses.
[0] https://en.wikipedia.org/wiki/United_States_debt_ceiling
Not to mention the majority party in the US House is threatening default.