i do think its okay to pay for points. The ones who spend getting a reward and the developers get their payment too.
But when it comes to lb, thats a no for me.

"If you're the competitive type, run for your spot on the Winter Event leaderboards" , this is the sentence under the leaderboard rewards heading of the preview post

If buying locks is gonna give these spots, then might as well remove the lb. just be plat tier and buy the event leaderboard lb vanities with plat. Or better, if they want competition on who can spend more, then set a total locks/massive opened count list and the first few people with leading numbers can get the reward. Would be an appreciation for the players spending the plats. Wont need the lb for the f2p players.
Winter would be the plat users event where f2p players just chill after getting plat tier rewards