I doubt it very much, but unfortunately I have never tested it.
The headphones are generally not very convincing, so I recommend buying ones that are compatible.
Or go straight for Bluetooth headphones.
Laut Hersteller: "Users with older OnePlus devices (3/3T/5/5T/6 ) must turn on OTG mode before using the Type-C Bullets (OTG Mode is accessible via Settings > System > OTG Storage. The OnePlus 3/3T will receive call function support by the end of November. The OnePlus 5/5T/6/6T/7/7 Pro supports all functions."
D.h. kein Problem mit dem 6T.
Unfortunately, the responsible supplier himself is still waiting for a subsequent delivery from the manufacturer and for this reason we cannot deliver it at the moment. As soon as something changes in this regard, the supplier will update the delivery date information.