It's not being changed arbitrarily. It's being changed by agreement. Holding 33% could make it difficult to raise money in the future I presume, which wouldn't

It's not being changed arbitrarily. It's being changed by agreement. Holding 33% could make it difficult to raise money in the future I presume, which wouldn't be in anyone's interest (including the leaving founder). Every founder should be subject to a vesting schedule, of course.