I'm not sure if you're asking why they would do it in the first place or why they would remove it. I'm assuming the latter for this post.
I don't know specifics, but I assume there was a complaint about linebackers ending up on the boundary against wide receivers in some particular formation or specific combination of personnel and it was removed. tl;dr - idiot-proofing against people who always expect CBs to only guard WRs. Which, on PS4 makes some sense because the player acceleration is so ridiculous that you have to match speed with speed in that game.
It was something my brother in particular has been very frustrated about this year; in our PS4 league, he chose the Rams, and he wanted to be able to easily stick Jalen Ramsey over top of George Kittle without formation subs or changing his position (we have a second user who always uses SF and knows how to get the ball to Kittle). After whatever patch changed the way best-on-best worked, he couldn't get Ramsey to easily align like this anymore
unless he came out with one more CB than the offense had WRs. This is obviously is not a good idea against a strong running team like the Niners. So we were stuck with only linebackers and safeties guarding tight ends again.
Combine that change with pattern matching being turned off against 3x1 sets for most of the year (as to soundly discourage stuff like Y-Trips TE Over or Trips TE Verticals Y-Drag) and yeah it's been a frustrating year guarding tight ends defensively.