It's not a horrible idea, but generally you should be wary of helping a team you're likely facing in the playoffs for years to come. Also, 6'1''?? I mean come on, 6'3'' I can deal with. PAYTON PRITCHARD is also officially 6'1'' if that provides any context. If Bam set a screen on him, Garland would probably totally disappear like an eclipse or something and you'd momentarily wonder why we only have 4 players on the court.
I also think that Cleveland as a smaller market team is trying to shed established guys for cheaper players right now. Jarrett Allen is the guy they're trying to get off of now in anticipation of Mobley getting a big extension in 2 years and the CBA restrictions coming up. Does that mean Garland is an eventual casualty as well? Maybe, but they drafted him and I think they want to go forward for now and worry about it when Mobley's new deal hits. If they dealt Garland, I think they'd rather do it for defensive role player types that wouldn't cost as much, and maybe one young player with some potential.