I don't know what you call it, but I'd like to take an existing video with music and maybe use every 4th (or whatever) video frame without changing the music. As a brute force method, I accomplished this by:
1) Unlinking audio & video
2) Time-shrinking the video by a factor of 4 (or whatever). So, I'd take a 4 minute video, speed it up to 60 seconds then create a .MPG file that is fast & short.
3) Read in the new fast-short video & time stretch it to the original length.
4) Add back the original music
This worked, but it's a bit cumbersome. Plus, if 4x isn't the right speed-up, you need to start over - maybe several times. Is there a filter or something that accompishes this?
Your method of time-stretching /time remapping will work. Particularly if your intent is to play your video at 4x its normal speed.
Premiere Elements also has a feature for capturing every fourth frame or whatever built into it's miniDV capture software, if your video is coming from a miniDV cam.
Your workflow is about as good as it gets.
The other option would be to Import the AV file, with both Audio & Video (muxed), then Export/Share just the Audio (to be used later), and then un-link the Audio & Video (as you have done), Delete the Audio from that Timeline, and Cut the Video, as needed, maybe even Exporting a Still Image, at the chosen points. If one did the Exporting to a Still, then they could just either replace the Video with those Still Images (doing that as an Image Sequence allows some additional control), adjust the Duration (Time Stretch/Time Re-mapping should work fine, or one could adjust the Duration of Stills in Edit>Preferences, before Importing those Stills into a New Project), Import that Audio-only file, from the first operation, and combine them with a new Export/Share.
The exact method chosen might be dictated by the "look," that the editor wants.