Is it true we grow in spurts despite frequent continuous gains in strength?

I am on a new routine based on what I have been reading.

My routine hits every muscle twice a week on a push pull split with 2 sets per exercise, sticking to a tight rep range and progressive loading each workout(I have .25kg weights for this purpose).

The rep range is 6-10 reps and I have seen very good strength gains but when measuring my arms they haven't grown all this month.

Is this normal or should I change routines? I am thinking maybe its lack of sets.