Why not

There'd be no point in a season pass if you can just keep getting the loot once the season is over. At that point you just grinding the loot like another thing in the game.

Most people that play would have level 100 done in 2-4 weeks anyway. But what about all those large numbers of people say buy witch queen deluxe which includes the previous seasons that they cannot claim, Not fair on those people. They paid for all that but is unable to claim it. Once the season is over do people really care if others can claim all level 100 levels of loot when a new season has started and they are playing ./ grinding the new content. I would say just give it to them, Who cares.