I have tried doing it at my end, it's working fine and letting me drop the image in the center of the opened document. could you try resetting the preferences of Photoshop CC 2018 and share the results with us?
Even though I am not the only one with this issue... you want me to TEST and see IF resetting my preferences restores ONE broken function but definitely kills ALL of my other functioning preferences and the problem may still not be resolved???
Adobe really needs to look at the Preferences file concept and consider splitting things up so that a customer doesn’t have to redo everything to possibly fix one issue. Better yet, bring back the Sync Settings functionality that was available a few versions ago and killed off for really dumb reasons i.e., as told to me by Adobe Staff... some customers could not figure out how to use it and rather than move servers, it was just deleted.
As soon as I have time to waste resetting all the functioning preferences that will get wiped during this reset, I will think about trying this.
Sorry if you feel like you're being tested on, however this is a fairly new update and we have tried to reproduce the issue you are facing at our end and it's working as it should be working. I understand that resetting preferences takes the software back to factory settings If you have important plugins or settings defined then you can create a new user account on your system with admin privileges and try to launch Photoshop there and let us know if the feature works in the new account.
Sahil, I tested this on a Mac, dropping from the finder, and I could reproduce it also. I was helping TA a class at MAX and showed Meredith from Adobe, the issue also. Copy and paste worked to center, but not drag and drop. Just tested with BR, and can reproduce on a Mac.