It depends on how you came to WK itself. If it’s part of a comprehensive course, self study or otherwise, that you’re already doing then go for it.
If not, then I would stick with the recommendation. Not because it would “ruin” your learning to add stuff while you’re doing WK, but because you won’t have an idea of how much time WK takes for you on a daily basis and whether you have room for something else.
I started WK and Bunpro at the same time and quickly dropped BP at around Level 5. I just couldn’t allocate the time to both. I’ve only recently started doing some BP in the last month or so, but only a few times a week. I honestly can’t juggle any more given a full time job, family, life, etc.
The best advice I can give for additional stuff is to watch YouTube videos. It’s more passive and feels less like work.
Here are some good series to start with:
Cure Dolly’s videos provide an amazingly intuitive way to think about Japanese. The content is quite good, but some people are turned off by the gimmick of the voice and having a CGI presenter. The titles are also a bit click-baity, but I honestly prefer her method over Tae Kim or any of the others I’ve seen.
Cure Dolly Japanese Playlist
SambonJuku 三本塾 does videos entirely in Japanese but he speaks clearly and is much easier to understand for a beginner. He’s a good teacher and his videos provide a good way to watch/read if you turn on Japanese subtitles for the videos that have them.
Sambonjuku Beginner Videos - Very basic. A good foundation but you’ll quickly grow out of them.
Sambonjuku 日本語おもしろい Videos - Much more fun to watch, and more information. Watch with subtitles to supplement your WK.
Sarah K. is a professional translator and her breakdown of the pilot episode for the original Sailor Moon is a great resource for learning how Japanese in Anime is different from regular day-to-day conversation. She goes over how different characters talk and a lot of the contractions and shorthand that they use.
Sarah K. Sailor Moon Series - Fun to watch and very informative for Anime fans.