About the impact of grouping classes in multiclass classification [D]

Excerpt

A premise: I hope this question is "worth" of this subreddit, I did a decent amount of research before posting, I thought it was potentially interesting enough for it, but possibly not basic enough for r/learnmachinelearning . Is there any agreement/indication about how harmful (if at all) it is, in the context of multiclass classification, to group together multiple classes for which you may have for instance too few samples ? A practical example : imagine you're training a dog breed classifier