Actually, funnily enough. I grew up in Texas and customarily say "howdy" as a greeting, and I grew up using it just as you say. I found it confusing for a while that coworkers who weren't native English speakers, particularly those I hadn't met in person, would reply to my Slack "howdy" with something like "oh, I'm good, thanks for asking". It was very jarring, like I said "hello" and they said "banana"; took me longer than it should have to figure out they were parsing the full "how do you do" since I'd never encountered that growing up. It became a pretty common experience at work.