If the media is in the same folder structure and the drive volume name is the same, it should not require relinking at all. If the volume name is different but the media folder structure is the same, they should all relink with a single step.
If the volume name is different, the media folder structure is different, and the filenames are not unique, that is a bad situation and it may require file-by-file relink.
Copying media files to another drive should not cause cause the frame count to change on clips. However media can be infrequently damaged during a copy, especially if over a network. That is why professionals use third-party tools which do a verified copy.
If a "new" file seems to have a different length than the original file, you can investigate that by examining the frame count of each one. For some media types, Quicktime Player will show you the frame count if you click on the starting timecode number at the left of the playhead. If the original media file is not available, you can export a clip XML of that file, then examine the duration of the clip, which is expressed as fraction, the quotient of which is the clip duration in fractional decimal seconds.
These steps will help avoid problems with media management and file relinking:
(1) Always be aware of whether media is imported via copy to library or "leave files in place". In general do not mix those types of storage.
(2) Only put FCP media on APFS or MacOS Extended Journaled drives - not ExFAT or anything else.
(3) All media filenames should ideally be globally unique. That means unique across all projects you've ever done in the past or might do in the future. It is easy to achieve that by simply adding an incrementing serial number to each filename upon offload, using Finder's batch rename feature.
(4) Do not rename files after importing them to FCP. If the files are renamed, FCP will automatically reconnect to those -- provided the files remain on the same disk volume. FCP achieves that with "inode lookup", a feature of Unix-type filesystems.
(5) If it's necessary to rename media files after importing to FCP, change only the trailing part of the filename. In some cases FCP can do batch-relink of renamed files, provided only the trailing part of the filename is changed. See FCP User Guide under the heading "Relink clips to media files in Final Cut Pro for Mac".
(6) Do not use media files hosted on iCloud Drive. This can happen accidentally if the MacOS feature "Optimize Mac Storage" is enabled.