I thought they’ve done studies and shown that running with a weighted vest does not make you faster (or at least no faster than running the same mileage without the vest).
Crossfit may be a bit different since the workouts are prescribed 2x20 of X movement…and if you do it long enough with just your own bodyweight, it becomes progressively easier. On a bike we can shift though to create/reduce resistance…the derailleur is our weight vest.
Watts are watts and power is power. Maybe if the added weight caused you to push more power and train harder (without overtraining) it would be beneficial.