: Q: Is studying outside of WaniKani detrimental to the SRS learning process?
A: This has been discussed many times, and while there isn’t a definitive answer there is a consensus (see below). The idea is that the SRS depends on testing the limits of your memory, so studying in between SRS intervals and refreshing your memory prematurely could be harmful to your long term memory.
Some people think extra studying helps, some people think it hurts, and some people don’t think it matters. As has been pointed out, WaniKani already contains items (radicals/kanji/vocab that share the same characters) that essentially “pollute” the SRS system as you see related items before they are truly due, so no one can be an absolute purist. However, it seems plain that reviewing an item just before it is due could easily give you an otherwise undeserved correct answer.
The consensus is that specifically studying kanji/vocab outside of WaniKani is pointless at best, and counterproductive at worst. However, stumbling upon kanji “in the wild” while studying grammar or reading Japanese should be fine.