Freshly released AOSP developer changelog for the latest 5.1.1_r3 Lollipop update (LMY48B) suggests that there is only one major change as depicted in the lone commit for this release.
Bearing the record for the smallest changelog ever, the lone commit in the release notes invariably points to the forthcoming Android 5.1.1 update for Nexus 6 (aka Motorola Shamu), reports Android Police.
It is ascertained that the update will be a bug-fix update for devices using encryption services such as the encryption-based lock screen.
With Nexus 6 being the only device in its line-up that has missed the Android 5.1.1 update, it is almost certain that the forthcoming OTAs and factory images would be focusing on addressing all shortcomings with the 6in phablet, in the next few days.
As the changelog still lacks clarity about the cumulative changes from the previous updates, we can only hope that the release of Android 5.1.1 update for Nexus 6 will clear out the ambiguity.