That wasn’t the design engineer’s fault. It was the design engineer’s fault and the QA tester’s fault and management’s fault.
Hate to be that guy, but for something bad like this to happen, it’s never one person’s fault. Like the engineer who nuked the gitlab backup by mistake while production had been deleted. He didn’t lose his job and rightfully so, there were a thousand other issues that led to that.
Recently, YouTube started adding a tracking parameter to their share URLs, when using the “share” button on a video. With this, they can track who is sharing videos with who, and under some circumstances even how they are shared. The tracker starts with the question mark in the link you posted and the link works perfectly fine without that part.