Retainers: Class change vs. Job progression

[LuSnow]

Hello All

Just to be sure that I understand correctly: When we, as char, progress our class, let's say archer for example, we then later evolve into bard.

My question: For a retainer, it doesn't work like that? Even if bard is the "natural" follow up of archer, it's considered as a class change and we have to pay the 40 ventures for the Modern Vocation?

Thanks for confirmation (or correction in case I wrongly understood).