Mine did the same. I put a plastic bag over the allen wrench and pounded it in, worked like a charm. If all fails fill the plug with JB weld and pound the hex key in, let it set up and that will work for sure. Do NOT cut or grind anywhere near that drain plug. The metal is so soft anything you touch by accident is getting scraped up.
Here we go @Rocket Scientist the original sump pan area of the tank plug (yellow box) oil plug (red line) and oil cross over port with the hole the O-ring on the plug seals up in (red box)
You can see the only real changes were the screen location and oil passages between and they did move the oil plug location a little bit. But when you look at the bolt hole patterns and the porting area where the scavenger pumps transfers they are the same. Of course they changed a few of these on early bikes (updated) I think most of it was to insure one of the pumps could scavenge oil no matter which way the bike was leaned over. Of course this is just my opinion but thanks for making me take a closer look at it Let me add a view of the newer style for comparison.