Bonus points for the vocabulary word.
some vegans have an issue with the word flexitarian because it is so vague. But its just another word based on the intent of a person. In this case, the intent is to eat mostly plants.
A flexitarian diet is becoming very popular in the UK. Here is BBC's GF definition which isn't vague at all :
Following a flexitarian diet highlights an increased intake of plant-based meals without completely eliminating meat