That’s actually WAY more likely than not. Concurrent invention is extreeeeeeeeemely common. Inventions occur almost as soon as it’s POSSIBLE for them to occur, and as soon as it’s possible for something to be invented, it’s extremely unlikely that only one person will think of it.
Consider how many times concurrent invention has happened: Westinghouse / Tesla / Edison, Coke / Pepsi, hundreds of automakers in the early 1900s, even more recently Microsoft / Apple, Betamax / VHS, HD DVD / Blu Ray. This is a short version of the list. Any new technology has a half-dozen also-rans that were near identical to the eventually-dominant product.
I think it’s more likely that two or more people had the same idea at the same time, than one person had the idea and everyone else “copied” them.