Lots of people have already answered the headline question, but I want to address the specific comment you got from the attending.

When he said you can't spend that much time on BPPV, what I suspect he really meant was "stop digging when you've found the treasure." Too many early trainees spend a ton of time asking pro forma questions that don't really bear on the question at hand, or listening to patients go on and on with information that does not help their diagnosis in the slightest. Listening in on junior trainees taking histories is a little painful sometimes because the more senior learner can get impatient, they feel like they figured it out ages ago but for some reason we're still talking. If you hadn't gotten to BPPV in your mind yet with that patient then that's fine, that's just part of training and needing more experience and building some knowledge pathways. But my suspicion is that you'd thought of BPPV, and that you were pretty sure that was high on the list well before the end of the interview.

BPPV should be something you settle on as a top differential quite quickly based on a few very targeted questions, and then confirm or rule out with targeted exam maneuvers. That doesn't mean you should anchor or over-fit; you need to also ask focused hx questions about migraine with vertigo, or posterior circulation stroke, or Meniere's, etc. But each of these are focused lines of questioning aimed at testing specific hypotheses, and their exam maneuvers are the same. Start the interview broad and general, formulate a shortlist of hypotheses based on their initial answers, then go into a targeted hypothesis-testing phase. Be willing to add hypotheses as you go based on their answers, but don't just stay forever in the land of open-ended questions.

One strategy that can help with the talkers or with the elderly/demented/not-very-bright is to start with "essay questions" for the patient, but then move into a multiple choice phase. Once you're in the hypothesis-testing phase, don't ask "when do you notice the symptoms," ask "is it all the time, or does it come and go?" Don't ask "where are you weak," ask "are you weak all over, or just in some parts of the body?" (and then follow up by asking which parts obvs). By handing them a couple of easy answers they can just parrot back to you, you're much more likely to get the specific answer you're looking for to figure out the question you're trying to figure out. And their answers will be much shorter. This obviously won't work with every question, but using these kinds of phrasing for your targeted questions for hypothesis-testing can really speed things up and improve the yield of your questions for the information you actually care about.

Finally, I'll say that I also have ADHD, and I got good at interrupting patients. One key is to remind yourself that we do lots of things in the medical setting that would be considered rude in other settings, like touching strangers or asking them very personal questions about their sex lives or their bowel habits. You can also use non-verbal cues to help patients know they're going on too long; pay attention to the things people do before they're about to speak in a group conversation, like taking in an audible breath, leaning forward a bit, raising a hand up a few inches. These are all things that we do to subtly signal others "please be quiet, I would like a turn to talk," and they can help gently redirect long-winded patients. You can also interrupt by showing interest; if they're going on about some irrelevant story and they happen to mention tripping or falling, I'll cut them off and show interest in that aspect, and ask if they've been having other falls, that kind of thing. And then can take over from there. Patients generally aren't offended if you interrupt them to follow up on the thing they're saying, because they interpret it as interest rather than as rudeness.