Update: As it turns out, it's a little more nuanced. If you are in the Slow or Fast Rings, the app now says "Go to Settings" instead of "Get Preview Builds." That's because the latest Redstone releases move Insider Ring options directly into Settings like on PC. In other words, this app merely reflects the new reality of the Redstone Insider program. For those who just want Insider Preview Releases (non-Redstone), you can still use this app to do just that.
A small update is currently rolling out to the Windows Insider app on Windows 10 Mobile.However, the update looks to be a relatively minor one with no outwardly visible changes.
If version numbers are your concern, this latest update bumps things up from version 188.8.131.52 to 184.108.40.206. If you happen to count yourself among the millions of Windows Insiders, you can go ahead and grab the latest update to the app now. If you aren't yet an Insider, however, you can download the app to enroll your device in the program with just a couple of taps.