if you deploy reversers with the nosewheel in the air, you are likely to scrape the reversers on the runway.
all MD80 operators admonish their pilots to never deploy reversers with nosewheel in the air
Not true unless you have at least 8 degrees of nose up - which CAN happen, but you really have to land slow and flare like a mofo for that.
At typical weights and flaps 40, you will not scrape a bucket. However, in the interest of training to the lowest common denominator and standardization, it is true that most if not all 80 operators require nosewheel contact before deploying.