Paul Braverman, who covers the AAA Fresno Grizzlies, had this to say about it:

Roughly 7% of MiLB games went to extra innings last season. One goal of this rule is to eliminate taxed bullpens; more specifically prevent position players from pitching, and reduce the shuttling of relievers back and forth between affiliates only due to innings count.

I don't love the rule change, but when you consider that the minors are for developing players and long extra-inning games are a huge headache, I guess it kind of makes sense. I don't see the rule ever being used in actual competitive MLB games.