An online retailer has posted a pre-order page claiming to list all the details on the upcoming OnePlus 6T, release date included. it describes a device with a teardrop notch, the Snapdragon 845 and triple cameras. However, some details on this 'leak' do not add up.
https://www.notebookcheck.net/OnePlus-6T-s-full-specs-have-been-leaked-or-have-they.331394.0.html
Seeing as how previous OnePlus phones borrowed just about everything from an OPPO phone.. it makes a lot of sense. Specifically, from the R-series.
So OP6T will have basically the chassis and features from Oppo R17 Pro and then paired down with a Snapdragon 845.
Oppo's VOOC and OnePlus' DASH are the same things.. just branding.
Oppo, Vivo and Oneplus share the same parent company and basically design their phones together.. they are all variations of each other and BBK has a single supply chain.
So no.. it's not surprising at all.