Maybe it's trendy to wear fleece pullovers among the missionaries on his mission.
Most missionaries don't obey all the rules. In fact, it is impossible to obey all the rules in the white handbook because several of the rules contradict one another and cannot be obeyed simultaneously.
I remember two "apostate" items of clothing that were very popular in my mission: green suits and wide, polyester ties. Both items were eventually expressly outlawed by our mission president, and probably never were permissible under a strict reading of the mission rules. But missionaries continued to wear them, not because they were individualistic but because it was more important for them to be "cool" in the eyes of the other elders than it was to be obedient to the letter of the rules.
The forbidden item in my mission (anaheim CA) was cotton pants. Our MP gave several sternly worded warnings to the missionaries that cotton pants were inappropriate and wearing them would not be tolerated. It pissed me off then, but makes me laugh today.