First of all, when one is “stepping into the ball”, the most ideal stance is squared stance and not closed stance.
Secondly, the benefit of stepping into the ball is to gain power as a result of weight transfer and linear momentum. It also ensures aggressive court positioning and takes time away from the opponent. Loading on the left leg in this situation can help with power due to the kinetic chain but also ensures that one is balanced prior to contact. I’ve seen too many players still with their front foot in the air as they try to make contact which results in inconsistency.
As for the opinion that open stance should be used more often than closed stance or squared stance, this is certainly true for the pros. This is due to the depth and pace of balls they are receiving.
When it comes to recreational players, I think it depends on age, as well as physical limitations. Open stance is much more demanding on the body and if you have someone who cannot put weight on their right leg, the linear momentum from stepping forward can help otherwise weak players gain depth as well as power on the shot. If someone has trouble rotating their body, then open stance is useless and even harmful to the body itself. In this case, there might be recreational players where hitting 70% of the time square stance and 30% open stance is actually more beneficial to them, even though the pros hit 80% open stance and 20% square/closed.