Yes. A poorly constructed carbon offset could be a form of greenwashing if it doesn't have the attributes of additionality and permanence. Not all offsets lack those things, but some do. It could be argued that those that do not have those attributes of additionality and permanence are de facto greenwashing. If you design the offset well, then no, it wouldn't be greenwashing.
On May 9th, 2024. See this statement in context.