Low sprocket_Max. 36T
Thanks for pointing that out.
Shimano is conservative though.
Many people use wide range cassettes with success on Alivio's. Now I don't know if the REI bike comes with long cage version, here is one member from here who switched to 11-46 on his Alivio 9 speed long cage(Shimano rates this for 36T max too).
But I understand your point, yeah one should ask around to make sure that things will work fine before committing.