This is the same as saying that a tax cut with an expiration date should be treated as if it were permanent.
Are you not aware that these things are different? That there is a difference between an adjustment to a proposed budget and a budget that has been enshrined in law?
What's the magical time horizon that changes this? If I change the taxes due for 2026, is that a tax cut? How about 2027? Where's the line between a change in law that is or is not a tax cut with this philosophy?
If you want consistency, a change in law that adjusts the tax burden downward from what the burden would be without the change in law is a tax cut. Therefore, a change in the law that makes previously temporary reduced tax levels into permanent reduced tax levels is a tax cut.