You said this:
Why do people keep saying this like a hard and fast rule. So a 2030 1st is equal to a 2026 5th

It was a loose over-exaggeration to try and value future picks. In reality, a mid 2nd in 2027 is probably closer to a late 2nd in 2028 than it is a 3rd and trades bear this out. But even if you want to agree with the dropping a round when it moves back one year, you can't do it for multiple years.
Would seem that the Cowboys org is thinking the same as me.
Per SI: The two sides talked into the night, and Dallas’s willingness to do a trade without having a contract extension in place helped finalize the trade. The Cowboys viewed giving up a second-round pick two drafts from now as giving up third-round value, and put a play-time condition on the sixth-rounder to protect themselves in the short term.