I used to have straight hair i think I have wavey hair now and I take care of it very well but not every day so I think this guide has some truth but it's ancedotel , not bad tho
I think you should have a day where u take care of your hair I take one day where i put oil in my hair and do other stuff too and it's really beneficial,I recently tried the thing where u put egg in ur hair so that the proteins in the egg helps your hair i thought it was kind of weird but it worked pretty well ngl