Not only is it typically not immediately vested for founders, but it's not totally uncommon for future rounds to "unvest" founders.
E.g. let's say you raise your A after 4 years, the terms of the round might require that you unvest 2 years so that the investors have you locked in for longer, to avoid the issue discussed in the original post.
E.g. let's say you raise your A after 4 years, the terms of the round might require that you unvest 2 years so that the investors have you locked in for longer, to avoid the issue discussed in the original post.