This makes sense, it was first Thomas who arrived on Sodor, then Edward. No one but just them running the railway before Henry, Gordon, James, Percy and the rest came along.
This can be backed up by the Island of Sodor book …somewhat. In that book, the reason why Thomas got to be Number 1 is because he was the first officially purchased engine for the NWR. Edward was purchased sometime later from the Furness Railway. But that still doesn’t explain why Thomas didn’t appear at all in the first book even though he was the first character to be created in the form of the iconic wooden toy made for Christopher. Maybe Wilbert was unsure about how to write him into the stories, or perhaps the Middleton didn’t know about him yet, but even in the re-drawings done by Dalby, he doesn’t even appear in the background. Guess this’ll remain a mystery for a long time…
This is very interesting Edward arriving on Sodor in 1915 as a hot-head in his express years, before he was left in the shed forgotten in 1923 because of newer engines or in this case… possibly punishment ??