This is not true actually. Since some kanji are blocked by the radicals for most levels, as long as you do all radical lessons right away, and all kanji lessons by the time you guru the radicals (which takes at least 3.5 days), you can still level up at max speed. You may want to look into [Userscript] WaniKani Lesson Filter and create a schedule for doing your lessons. If you want to level up at max speed, I’d recommend something like this:
- Day 1: All radicals, 1/3 of unlocked kanji, some vocab
- Day 2: 1/3 of unlocked kanji, some vocab
- Day 3: 1/3 of unlocked kanji, some vocab (all kanji lessons should be done at this point)
- Day 4: (radicals hit guru) all kanji unlocked from radicals
- Day 5: 1/3 of unlocked vocab
- Day 6: 1/3 of unlocked vocab
- Day 7: 1/3 of unlocked vocab (all vocab lessons should be done at this point)
This script is powerful, but you have to use it responsibly. Don’t neglect your vocab lessons or you’ll just hurt yourself in the long run. If you can follow this approach well, you’ll level up just as fast and still learn all the content, but you’ll have a much more balanced lesson and review schedule, which should remove some of the pressure.