Is this an intentional reference to the removal of both of these keywords as evergreen?

Yep... They can still be in expert level expansions, right?

They're technically allowed, although landwalk has been mostly abandoned anyway and protection (other than one turn effects) is never at common.

Instances of common protection in Modern for more than one turn: Azorius First-Wing, Diregraf Escort, Enemy of the Guildpact, Goblin Outlander, Grave Bramble, Guardian of the Guildpact, Guildscorn Ward, Harbinger of Spring, Kitsune Riftwalker, Midnight Duelist, Nacatl Outlander, Nacatl Savage, Nath's Buffoon, Pentarch Ward, Ronom Hulk, Tel-Jilad Archers, Tel-Jilad Chosen, Tel-Jilad Fallen, Tel-Jilad Outrider, Valeron Outlander, Vedalken Outlander, Warren-Scourge Elf, Zombie Outlander. Most recent is Guildscorn Ward from DGM.

I was only looking at Standard. A bunch of those are either trinket text or strongly related to the set's themes.

I like protection, so I'll use it sparingly, but I think I want to keep it around for now.