What is new here is landing on the smaller combatants, such as this DDG. This is a much more difficult job: there are many nearby masts that must be avoided, the landing area isn't much larger than the helo, plus the ship's movements are much greater. Indeed, the landing is so difficult that often Navy helos do vertical replenishment (VERTREP) where they hover over the ship and pass the cargo to the ship using a winch and a line, rather than landing.

This is not a simple qualification of learning a few new Navy procedures and terminology (as it mostly is for the big decks), rather this is a much more challenging skill, in which the pilot must keep proficiency. And because of that proficiency need, I doubt most Army helo pilots will get qualified. A few pilots will get qualified (and maintain proficiency) on an as needed basis.

However, there are quite a few more DDGs than there are carriers, so this is a good skill to have available.

My bottom line here is there is a big difference in the skill level between landing on a big deck versus a DDG.

google is your friend.