I think the answer depends on the manufacturer's suggestion for their particular light fixture. Most that I've seen won't warrant any failures if you don't use a glass canopy below the fixture. You also need to be aware that many 'knock off' brand fixtures aren't water resistant or possibly even UL or similar safety rated.
Eheim Pimpette #270
Eheim Pro II 2028; Classics Series -2215, 2217, 2260, 2262; Pro 2229 Wet/Dry
Yes, bare LEDs are vulnerable to moisture ingress, even from condensation.
I lost a few bob having to replace ≈ 12ft of 5050 LED ribbon because the LEDs drastically lost their intensity within a few weeks above the open water surface.
I replaced them with ribbons that are hermetically sealed in a clear plastic tube.
My LED light has no splash guard, and sits about 2-3 inches above the water. It has been in constant use for over 2 years now, with no problems, and no visible deposits on the LEDs. I don't have any rising streams of bubbles in the tank - no airstone, and no CO2 mist. If I had a strong airstone flow of bubbles I suspect there would be problems. It is bursting bubbles at the water surface that "splash" the lights. (My opinion.)
LEDs themselves are for all practical purposes 100% waterproof indefinitely. Their associated electronics however are quite succeptable to moisture damage due to their use of high frequency switching. Just keep condensation off of direct contact with the contacts/components and you'll be fine for several years. Keep everything away from humidity and you'll be fine for the life of the fixture.
People are too often merely stating an assumed truth from flawed observation.