I looked into this, and this is the reply I got from LSAC:

"The change went into effect starting with the June 2017 LSAT, and the reasoning is simply that the official time is kept by the room supervisor. Timers of any kind are not permitted. As stated, non-digital, analog watches are permitted in the test center. This would be the traditional kind with an hour & a minute hand (seconds hand is fine as well) whose purpose is to tell time & not to time something with a dedicated start/stop functionality. With this in mind, the 180watch would no longer be allowed, however the Casio, Top Tier, and Perfect Score watches would be permitted."

I thought this would be helpful for everyone to know!