Here is another data point, probably doesn't mean much since it was back in 2000.

I know a guy that got an interview and got hired at United in 2000 with no rec letters. He was just the AWG captain at a large regional and zero jet time. A friend of his at the same company had 2 internal recs and a lot more PIC time and he never got called for an interview.

The word on the street at the time was United used a point system, you got points for every category on the app. For example 121 PIC time was worth more points than FO time. The un-official word was that you got one point if you had a internal rec and it didn't matter how many you had, you still only got one point.

I don't have any idea what they do now but it would make sense that rec letters only count as a small part of what gets you an interview, otherwise the people with 10 or 20 letters would be getting all the interviews and that is not the case.