The way I see it, it’s all to do with progression.
Example 1: Dude only does isolation exercises. His barbell overhead press (if he ever did it) is about 135lb 1RM. When he does lateral raises he uses the 14lb dumbbells for 6-10 reps. He has gone up in weight slowly over the past 3months but lately going to the 16lb DB’s has made him drop below 6reps.
Example 2. Oldmate likes compound movements and only does isolations when he feels like it. His OH Press has gone 95lbs to 135lbs in 2 months due to smart loading and progression. When he had a 95lb press his lateral raise was 12lb for 10reps. He tested it again and found he could pick up the 16lbs and repped 8 of them.
Because Dude can only micro load small muscles, it makes it harder for him to progress. Oldmate focusing on larger muscle groups finds it easier to progress his weight and therefore finds he is stronger when he goes back to isolation.