It's not a bug. It's intentional. A small percentage of the playerbase cheats in puzzle rush. The leaderboard would be an absolute mess without the titled restriction. Cheating in puzzle rush isn't detectable, so chess.com has to use other criteria to filter out the frauds.
Sucks for sincere puzzlers (my 55 score ), but I get it.
They are def capping it at 49 for untitled players, just look at this ridiculous leaderboard:
This has happened to me as well; having just scored a 50 on five-minute rush, my score is showing for me but is not visible on any leaderboards.