whoops I’m sorry for how long this is but I wanted to make sure I was at least a little bit helpful…
The short answer is yes, it will, but it can be a bit more complex than that. WK is based off of the SRS method, which regulates what I think of as study exposure (as opposed to seeing it in the wild). If you were to study them on your own time, you would be essentially changing the SRS intervals as you’re studying the vocab closer to when you’re seeing them again in WK. This sorta defeats the purpose of having the intervals in the first place, which attempt to cement the word/phrase/etc into your long-term memory. You might progress them faster, but then the word may not stick in your head and that’s not helpful.
That being said, this isn’t a reason to avoid consuming Japanese media with learned and unknown vocab/kanji in them. If you’re reading a manga, for instance, and you see 三日, that wouldn’t really count as messing up the study intervals, right? Or if you see 勝負 and you learn it then (a level 9 vocab), that’s not the same either. And seeing it in that context might cement it more in your memory than just drilling it in WK. And personally, I’ve studied kanji and vocab I have problems with via the self-study script, but I do so right after the review or lesson where I had the issue to try and keep the intervals close, but only in a few limited cases.
If you mean more that you’d like to study upcoming vocab before you take the lesson, then I would be cautious about that (but that doesn’t necessarily mean you can’t). You’re at level 5 now, so just know that things are about to get a bit more intense pretty soon (not bad, just more involved) as items start to cycle back so you may not have that much extra time to put into studying more vocab without burning yourself out. It’s up to how your schedule is. Also, you may want to use that time to instead study grammar and the like, and practice listening and talking. Just another recommendation, as I’ve found that it helps me to hear a word in a more natural setting than a flashcard. Also, it’s an excuse to do more fun things than flashcard drills
So I don’t think it’s necessarily counter intuitive, but I would recommend maybe just stepping up the amount of vocab lessons you’re doing to a comfortable level and adding some other resources, like anime, manga, graded readers, dramas, etc. There’s some really nice beginner bookclubs here that are great for that!
I hope some of that was at least helpful! Best of luck, I’m cheering for you!