I think anyone who speaks about monolith today assumes you do use modules appropriately.
I mean for "starting with a monolith and splitting out when necessary" you kind need property structures code (i.e code which uses modules and isn't too tightly coupler between them).
Through in my experience you should avoid modularizing code with the thought of maybe splitting it into parts later on. That's kinda defeats the point of starting with a monolith to some degree. Instead modularize it with the thought of making it easy to refactor and use domain logic as main criterium for deciding what goes where when possible ( instead of technical details).
I mean for "starting with a monolith and splitting out when necessary" you kind need property structures code (i.e code which uses modules and isn't too tightly coupler between them).
Through in my experience you should avoid modularizing code with the thought of maybe splitting it into parts later on. That's kinda defeats the point of starting with a monolith to some degree. Instead modularize it with the thought of making it easy to refactor and use domain logic as main criterium for deciding what goes where when possible ( instead of technical details).