non cumulative differential backup for SQL Server
Transaction log backups are incremental, that is, they only store incremental changes since the previous transaction log backup.
And they do it more or less as you told, using last well know backuped LSN (a checkpoint).
This is why you have to restore the full backup and then all the TLOG backups in the proper order.
But this requires full recovery model. Differential backups work in all recovery models, namely Simple, Bulk-Logged, and Full.
If you want incremental backups (i.e. non-cumulative differential backup), take transaction log backups regularly.