Whilst many software applications can share metadata via XMP files, the situation is far from a recognized standard. XMP is an extensible XML style format, which means it can be customised. Applications that read this data, need not be able to understand everything. They just need to honour (and not modified) any such data. Adobe itself use the XMP the file to store details of proprietary Post Processing methods within Lightroom, These methods are unlikely to be known by the software, and that software should not be expected to reproduced the exact Lightroom process. Corel’s Aftershot Pro also uses its own proprietary XMP format for its processing, but also offers the opportunity to save standard XMP files by which it means just the metadata.
Is in the area of metadata that there does seem to be good agreement between packages. Specifically key wording, star ranking and the colour flags/patches or classifications do seem to be reliably exchanged between programmes. Most of the EXIF data seems to be so exchanged, when exception might be camera settings and lens identifies (usually of read from RAW files) that don't always make it into XMP files. Some some software does not acknowledge IPTC metadata.
Finally I don't expect to be told what isn't read from and XMP file. Anything that isn't under stored get ignored. So for example you may have set the Likes and Dislikes in OnOne's perfect photo suite, but they will not be interpreted as Flag as Pick or Set to Reject in lightroom so they just don’t show up.