x2 all of this.
Not having an "arm day" is not the same as not training arms at all. There's the classic idea that "the biceps get a bit of work with back exercises, so finish off the day with curls and some more bi work". Back/bis, chest/shoulder/tris, legs (quads/hams/calves) is one of the most basic splits for a reason. You're still giving arms direct attention to get them to grow, but you don't have one particular arm day.
There are lots of ways to arrange things, and the "best" choice will be influenced by the lifter's current development or lack thereof, their goal, available schedule, etc.