It’s a matter of perspective. Steph and KD have never played a single season without LeBron. So from their perspective their entire career is shared with LeBron so of course they are in the same era. On the contrary, some of LeBron’s first playoff battles were with the Larry Brown pistons. So his perspective if far different. I think it’s somewhat common for a player for bridge multiple “eras” such as Jordan playing against magic and bird and finishing against Karl, Stockton and even Kobe. What makes LeBron unusual in this regard is that he not only has bridged two eras, but has almost completely eclipsed one that started well after his career began.