Slide rooms and Leveling

This depends on the manufacture and how the slides are installed. Some are , slides out then level. You wouldn’t camp hopefully in some crazy out of level place. If you are someplace the levelers are capable of leveling you you are ok. I was told that if I didn’t do it that way on mine , like yours that slides go out first, I could damage the slide outs! It doesn’t seem normal to me asl the other brands I’ve owned were reverse of that , but I was assured the slides were made to be operated while out of level and fully aired up.
Follow the manufacturer method .. whatever that is for you coach , they aren’t all the same.