Because it was BROKEN and people started abusing it.
It was likely unintended and players were using it as an exploit. Directly against the Terms of Service. I’m sure we’ll see a more thorough post outlining the details tomorrow.
A change in progression is addressed as a possibility in this post announcing the reworking of acts 1-4: https://forums.playcontestofchampions.com/en/discussion/286114/the-prologue-initiative-a-fresh-take-on-acts-1-4#latestIt reads: "However, if you have not fully explored the Act and some of the paths you have completed were removed, you may notice a change in your completion percentage."
Still doesn't look like anything changed from how they were before the update to me either.