Thanks for bringing that to our attention.
Here’s the language from the Democrats at the time justifying Trump’s impeachment:
In addition to establishing the Congressional Budget Committees and the independent Congressional Budget Office, the Impoundment Control Act also limits the circumstances under which a president can legally impound Congressionally-appropriated funds.
According to the Act, although the President may request authority from Congress to withhold or permanently cancel the availability of budget authority, such an action is not allowed without Congressional approval. Any amount of budget authority proposed to be de-ferred (i.e., temporarily withheld) or rescinded (i.e., permanently withheld) must be made available for obligation unless Congress, within 45 legislative days, completes action on a bill rescinding all or part of the amount proposed for rescission. The Impoundment Control Act does not permit the withholding of funds through their date of expiration, which would be a de facto rescission without Congressional approval.
https://www.congress.gov/116/crpt/hrpt335/CRPT-116hrpt335.pdf