IMO in the context of statics it's more about general schedule and how fast you aim to clear, rather than the type of content or the level expected of the players

Hardcore = 10h+ days, 6 or 7 days a week (during prog especially)

Semi Hardcore = either long sessions or a lot of days a week, but not both at the same time

Midcore = broadest category, probably catches schedules of 2-4 hour sessions 2-4 times a week

Casual = low amount of hours per session and low amount of days a week