Right, but zero? I can’t study Japanese words at the moment without interfering with German.
If your learning goals are mostly focused around reading, it's helpful a bit.
If you want to actually understand and use the language, hiragana, katakana, vocab and grammar have much higher utility.
My most complete advice would be to focus exclusively on the language you’re learning and don’t futz around with half-measures, but who am I to tell you what to study? If you’ve gotta satisfy the itch, then sure, you might learn something.