Some players struggle to keep the weight on and other struggle to keep it off.
Scott may be one that always found it difficult to maintain the weight. By trying to maintain that weight the value achieved was offset by the speed lost,
when he was younger and faster, the offset was negligible, it is no longer so in Rex's and his opinion.
Mass/Velocity Physics aside, The hit you deliver is based on you technique. Guys like, Atwater, Lott, Lynch, Harrison were some of the hardest hitters on the field and only weighed #210-#220. This is the result of technique.
This is a good thing for the jets, He could no longer play at 250, and he wants to try giving it a go at 235, what's to lose?