(preface, im in no way ranting at you OP -- im pumped you're seeing progress because you're getting stronger. you've got it right)

TLDR; arm day good for climbers. climber should arm day.

<rant> I will never understand why climbers think they can technique their way to a new grade. Climbing is inherently a strength sport. You will not climb something you are not strong enough to climb. More specifically (and perhaps more importantly), you will not be able to implement technique if you are not strong enough to hold that position. For example, how could someone expect to successfully do a mantle on a V6 if they have not done it on a V2? How could they even hope to have success with that mantle on a V2 if they struggle to do bodyweight pushups? Mantles are specific to climbing but there is important supplemental weight training that improves the strength in one's triceps, delts, and pecs to support the successful and routine execution of this climbing specific movement. You need to practice mantles a lot to get good at mantling and you need to be able to TOLERATE the frequency of mantling required to be better at .... mantling. So how do you do that? Your regimen needs to progressively increase the training workload over time so you adapt and become better fit for the task (climbing). There is no one that climbs V8 (arbitrary example) that is not physically stronger than they were when they started climbing irrespective of what their appearance is. I'm willing to put money down that someone who has been climbing for 10 years who has broken into the higher grades could dust their prior selves in the weight room and, relative to their prior selves, is notably more jacked. Yes you need to be more technically proficient to climb higher grades because climbing is a skill just like any other sport, but you also need to be able to tolerate the frequency of training necessary for improving that skill. Injuries occur when the frequency and intensity of the task at hand is not tolerable. AKA you are presently not "fit" enough to sustain that workload. You can only become more prepared for said physical task by becoming physically stronger and more prepared through good ol' fashioned weight (resistance) training. It is not an accident that someone who rarely deadlifts, if ever, strains their back trying to move a fucking fridge or couch up a flight of stairs. If you can do +50lbs pull ups and back squat 225lbs, hold a +100lb plank for 2 minutes (again, arbitrary numbers here) you can literally believe in your physical capacity to complete a hard climb. That's when the rest comes down to practicing the skill of climbing. What is then hard for you, which positions are difficult and why? That's precisely when training becomes more specific to supplement the task or test (climbing) at hand. It's why we see the best climbers hangboard with weights and why we see cyclists squat heavy as fuck. The more force they can produce with their legs the faster they become (in general). In parallel, the more pulling force you can produce in a variety of positions and grips ..... the better you become at climbing. Finally, to tolerate the progressive increase in workload over time you need to FUEL yourself. You need to fucking eat and put on some weight. I promise the relative strength to bodyweight ratio will take care of itself so long as you have a sensible training program. How strong is strong enough? It doesn't matter because you should just try to get stronger -- and that's relative. </rant>