I assume that when you reveal a second card from the encounter deck to satisfy the 'guarded' keyword on an Objective, that card is treated like any other card from the encounter deck, i.e., Surge and When Revealed effects would be applied?

That's how I'd play it. I'd only attach the first eligible card drawn, of course. If any more cards are drawn using SURGE o-r using game text are just played in the Staging Area, as usual.

Yes, that makes sense.

I'll play it that way.