Can DLM remotely cause a resync to raise speeds?
Can it? Yes.
Does it? No, not exactly.
DLM remotely triggers a resync because it has changed some error-protection settings, and wishes to apply those new settings.
The change in settings may cause an increase or decrease in speed - DLM doesn't care. It just wants to get the new settings into operation.
DLM doesn't monitor your line to see if a re-sync could raise speeds for you.
DLM only monitors your error rate. If there are too many, it alters settings in order to add more error protection, in an effort to reduce the errors. If there aren't many, and error protection is in place, it can alter the settings to reduce or remove the error protection.