Faolyn
(she/her)
You once again failed to answer my question: if a PC who starts out with proficiency in medium or heavy armor--since there is no proficiency in metal armor--becomes a druid, do they lose that proficiency?The same future-tense verb applies to the proficiency too.
The Druids will wear nonmetal armors proficiently, but will not wear metal armors proficiently.
Again: there is no such thing as proficiency in metal armor. "Metal armor" is not a class of armor.