I would look at it the other way , If everyone were to send their Medicals then there will be further delays . If its not mandatory to send a doc to the USCIS then you might as well wait as sending more info delays things .
Honestly they need the Medicals only when the Final Action dates get closer and I hope they ask for them only when Final action dates are close by as Medicals can anywhere between 500-1000 dollars today . For a family of 4 that will be 4K and most companies don't pay for dependents .
In 2012 I paid $250 , in 2018 it was $550 , just for the doc to sign a few pages . My friend paid 950 last month in the Bay area.