Probably inconsistent is the wrong word. Here is what happens: if I do a metadata search of my current catalog (contains 2015 and 2016) and I look at the lens column, there is an "Unknown Lens" group. This works out to be some, not all, of the Sigma 50mm 1.4 Art lens images. For some reason they show up here as "Unknown." Yet, when I click on an image from this group, and go to the Develop pane, the correct lens does in fact show up in the Lens Correction profile.
One thing I was thinking is that, in my using a lot of manual focus Zeiss lenses, perhaps I left the camera set to MF when I slapped on the Sigma. Yet, the Zeiss MF lenses consistently show up correctly. Not a big issue, just a puzzlement...
Are you using a Nikon camera?
There is a bug in LR 2015.5/6.5 that doesn't report lens data correctly for some if not all Nikon cameras.
The data is in the metadata but LR isn't reading it or reporting it correctly.
Thanks. I am shooting a D810 and DF, so I guess that is the answer. Funny that the Develop Module actually sees the metadata correctly...
See this bug report for more details: Lightroom CC 2015: Lens metadata field missing on import | Photoshop Family Customer Community. Adobe has acknowledged the bug and said it will be fixed "soon", in the next release. If you add your vote and follow that topic, you will be notified when it is fixed.