Is it safe to run the Apple Watch Ultra under running water to clean it?

I’ve read apple’s guidelines for cleaning an Apple Watch -

How to clean your Apple Watch - Apple Support

In the first section, it states “Avoid getting moisture in any openings, and don’t submerge your Apple Watch in any cleaning agents.”

In a latter section, the support article states, “If your Apple Watch has substances or debris visible in places such as the speaker ports, you can hold your Apple Watch under lightly running, warm, fresh water until it's clean.”

Does the latter section mean I can rinse the unit under lightly running, warm, fresh water safely?

If so, why does the first section say to avoid getting moisture in any openings? Do they mean moisture from cleaning agents? What openings might they be referring to?