“They” has been a very common usage in a singular context for a very long time, certainly during the 3+ decades that I’ve been educate enough to even know what a pronouns is. This usage dates back the better part of a 1000 years to the 1300’s

Formulations like the following are common: “Bob saw someone shopping for the Dolphin emulator in the steam store on their computer. They couldn’t find it though because the litigious corporation Nintendo had sent a DMCA takedown notice.”