The following transaction logs will be based on the backup the developer made
Log backups are not based on a specific full backup (except when it's the first full backup made), so in your scenario the developer could take as many full backups as he likes and it will have absolutely no effect whatsoever on your recovery path.
The only thing that copy_only on a full backup does is to not reset the differential base
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: Discussions on DB performance with occasional diversions into recoverability
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