Apple's 3.1.2 list says functional links to the privacy policy and Terms of Use. Functional is the word that costs a cycle. Speech Route did not have a URL at all. A 404 is the same failure with a nicer button.
Functional means a page
I tap the link on the paywall. If it does not open a document a reviewer can read, it is missing. An in-app browser that loads blank counts. I wrote the file-versus-URL rejection as Guideline 5.1.1. The paywall side is 3.1.2.
Two places, one URL
The same address has to work on the screen and in App Store Connect. Doing Connect and not the paywall is still a round trip. Doing the paywall with a link that 404s is also a round trip.
What I do on a device
I open both links on a phone, not only in a desktop browser. Then I submit. The pre-submit list has this as a gate, not a later fix.