Was it intended for a lot of them to sound so suggestive and creepy? There's the classic wood elf male one that most players hear early in the game: "I have a feeling that you and I are about to become very close". And then there's the male nord "that's how I like it, bold and direct. Come, I like you!", and the slightly more innocent redguard female "any time you're ready, just don't keep me waiting!". Everyone seems to have awkward reactions from hearing these.

I mean, what were they thinking when they wrote this stuff?

They were likely thinking... How can we make all these different greetings memorable from each other, without breaking immersion or the style of the game?

What would you have them say? "Hey bro, want to go for a pint of flin?"

Bosmer are sly, so that line seems to fit. He could be suggesting some clandestine dealings.
The Nord line is perfect, because well... Nord are bold and direct and would want to hear what you have to say.
The female Redguard line (which I believe female Dunmer also say) is perfect. Have you never talked to a girl before?

Personally, I think the Dunmer reactions are the best. "Talk, please, my friend. You're nearly a legend around here!"

I have no problem with "I have a feeling that you and I are about to become very close." To me it's not much different than Humphrey Bogart saying, "Louie, I think this is the beginning of a beautiful friendship." People say these kinds of things from time to time. It doesn't mean they're coming on to you.

Actually, that is one they should have included.