geotagging - How do I get Lightroom (CC 2015) to only geotag pictures taken during timespans that have tracks in a GPX file?

After a holiday trip I want to geotag several days' worth of pictures. (The timestamps are already synced).

From my GPS watch, I successfully imported a .gpx track file, which contains several tracks of 30 min to 2h. But they don't cover all the photos, but only some timespans.

Problem: If I select all pictures (of my complete holiday trip) and use the LR command "automatic geotagging on selected pictures", the pictures that weren't tracked in the gpx file get geotagged on a virtual linear line between the last known coordinates (which is wrong).

So how is it possible to only geotag the pictures which were shot while I recorded a gpx track (without plugins)?

There are a lot of tutorials about this topic, but they all say: select the pictures you want to geotag. But I want to avoid selecting only a range of pictures; I want Lightroom to decide which pictures were shot during GPS track recording. This should be possible due to the available timestamp information (at GPS track and picture).