As @oldnapalm mentioned, it’s this feature - Introducing Leaderboard HoloReplays [May/June 2023]
From the FAQ:
How do I see other Zwifters’ Replays?
- Open the in-game settings and scroll down to “Leaderboard HoloReplay”, then set “Leaderboard HoloReplay” to “Show” (the default option is “hide”).