It's definitely a myth, or at least a minor contribution.
BetaMax housings were very small, so they didn't have enough capacity for feature films unless they were run at 1/2 or 1/3 speed, which reduced quality. The thing is, VHS could also be run slower to improve run times, but instead of maxing out at 90m, they could run for almost 250m for tapes about at the same price.
Tapes with longer run times eventually came to market, but well after VHS had established itself.
Something I've heard brought up regarding the length is that early Betamax couldn't tape the average sports game, while early VHS could. I'd imagine that was a big selling point.
The early Betamax recorders didn't have a timer on them. Plus the tapes were super short. So if you had a show at 3pm you wanted to tape, you had to be there at 3pm to push the record button, then be stuck with only 90 minutes of recorded content.
The first Betamax recorder sold in the US was the LV-1901 which included a 24 hour timer.
The first standalone Betamax VCR was the SL-7200 on which the timer was a $45 optional add-on.
Also at the time people were already buying wall socket timers for their reel-to-reel tape decks to record the radio, these would also work with a Betamax deck. https://www.youtube.com/watch?v=XbNgbtZJAcU
Highly doubtful. They were (mainly) “just” a telecommunications hardware/electronics company up until their purchase of Columbia Pictures in 1989; they wouldn’t have had an incentive to defend the entertainment sector in 1975 when Betamax was introduced.
This is something that is always mentioned, but sometimes I wonder if it is not a myth, or a simple exaggeration or simplification.