Thanks for the link! I think I understand what you’re referring to now. “Stress-timed” vs. “Syllable-timed” languages refers to the influence of stress in the time it takes to say words. It doesn’t refer to the presence or absence of stress as a whole.
“Stress” in language is an umbrella term that can refer to many characteristics outside timing, including reference to the syllable that “pops” in a word. For example, in the word 시간, even though the timing of each syllable is the same, the syllable “시” still has the pop. You wouldn’t put emphasis on the “간”.
A similar example to Korean is Hungarian. Hungarian is also a syllable-timed language, but it has non-phonemic stress. So, the stress has specific rules, and is predictable, like Korean. Unlike English, stress doesn’t have a phonemic property of the word in this case, but it’s stress all the same.
**Editing to add, I agree that the placement of the lips is different, contributing to OP hearing the “B” sound. I used “stressed” to describe the phenomenon as I thought it would be a simple, easy to understand explanation, and the actual name of the phenomenon escaped me. (ㅁ doesn’t always have that described “b” sound to it. The ㅁ in 미래 sounds more like an “M” than the ㅁ in 물. ) It is related to stress/aspiration however, but I probably should have figured out a better word to use.
**Edit 2 - There are a few inaccuracies in that iTalki article with words being used synonymously with unrelated ideas. It’s a good article overall, but it’s also just a blog post that hasn’t been peer reviewed.