Bicep training for Strongman is a hot topic, I feel some type of direct bicep training is important for a few reasons most of all is injury prevention. The other cause of bicep injuries can be overuse injuries.
If you were already following a bodybuilding style program then throw Strongman training into the mix you just added on a ton of volume for the biceps and it probably won’t recover.
Tire flips, log cleans, atlas stones, arm over arm pulls, etc.
You have to account for the added volume added!
if in more of a general strength phase with less actual implements more direct bicep work should be done, closer to a contest you will want to save that energy for the actual contest implements.
some light high rep curls of 2-4 sets 1-2x a week should be plenty for most phases and programs