I feel you still have a fundamentally backwards understanding of how nutrition works as it relates to training.
You don’t eat a calorie surplus and then hope it turns to muscle via training: you TRAIN for muscle and then eat a calorie surplus to recover from that training and ensure that it happens.
If your training is not putting any sort of demand on your body to create more muscle, THAT is how you get fat from a caloric surplus. That’s what most people do, irrespective of training: they eat more food than their body needs to recover from the tasks it has performed.
When gaining muscle is the goal, you start training HARDER than you had before, so that you create a new demand on your body to start making more muscle as a response to the stimulus placed upon it. If you don’t create ENOUGH stimulus through training, your body has no need for a surplus of calories, which means that the surplus you eat simply becomes fat: it’s excess calories with no purpose.
I feel that, if you focus more on training hard enough to create a demand on your body to make muscle, you’ll have far more success with making muscle and getting less fat compared to if you concern yourself with the degree of surplus you have. In truth, I would not eat a surplus UNLESS there was a specific need to do so: in this case, stalling or regressing in lifts or a lack of recovery from training in general.