I have noticed that, at least with Prism Array, but I think it is the same with the other landfall cards, the landfall does not trigger when matching 4 or more planeswalker runes.
On the opposite, Part the Waterveil triggers when matching 5 or more planeswalker runes.
It’s a new bug for Part the Waterveil, to me at least. Loyalty matches of 4+ never triggered anything that has “landfall” on it for as long as I’ve been playing and that’s how it’s supposed to work. So I’d say report that interaction as a bug.
Also, most decks using Waterveil have a LOT of ramp cards in them. Are you certain there wasn’t a separate landfall on the board at the same time of the loyalty 4+ gem trigger? Recreating the scenario in video is always useful.
I just read the cards to be certain. Part the Waterveil reads “Whenever you match 5 or more gems…” which wouldn’t necessarily exclude loyalty. “Landfall” definitely excludes loyalty.