Arms day and overtraining

I see many people training bi’s and tri’s on a separate day from back /chest.
Wouldn’t say closegrip bench on tri day and then full bench for chest day in the same week overtraing the chest or tri’s? Same with back and biceps, like… do chins for back one day then curls etc. on another… don’t you overtrain the bi’s? I don’t get it

It is unlikely because the Bi’s & Tri’s (Arms) are small muscle groups that require minimal recvery time. They can be trained up to 3 times per week-directly or indirectly.
The same could be argued for the chest which some people hit twice per week…