What was their reasoning for that? I've thought about Alaska as well, and would like to know.
Further into June you go the wetter it is likely to get apparently.
More dry days in May as long as you do not mind a few degrees cooler on average. I am good down to mid 40's Fº without heated gear and down into the 30's Fº with heated gear so the slightly lower average temps do not concern me.
Apparently you are also likely to see more of the season change with more blooms and more prevalent wildlife coming awake after the long winter. His opinion was that the best time to see things like brown bear was the last two weeks of May.
Apparently the flies and mosquitoes get worse the later in the season it gets.
Finally, June 1 apparently begins the infestation of Alaska's greatest nuisance pest, the recreational vehicle.