Could mean "I didn't know you had so much stuff on your plate that takes precedence". You're giving 0 benefit of doubt to a PM who in my opinion was right to push back because for a non-technical person it's not easy to grasp why drag and drop should be so much harder than other similar impact features.
Ah and there's the rub. Why should a PM of a software project even be a 'non-technical person' (because tbh what's even the point, how would a 'non-technical' person even be able to evaluate technical decisions and their implementation?). And even for multi-disciplinary projects like videogames it's not too much to expect that the project manager has at least a basic understanding of all crafts that work on a game.
E.g.. there's nothing more useless than a PM that's just pushing task bars around in JIRA to make them fit into the next sprint.
...and also: would you fly in a plane, or drive over a bridge that was built under supervision of a 'non-technical' PM? (I know I know... since the Boeing disasters that question is rhetorical, most people don't seem to care)
The head of a space program doesn't need to be an astronaut. An admiral doesn't have to know how to swim. A PM doesn't have to know all the various engineering disciplines the project may touch.
The comment was derisive, and therefore poor leadership. Period.