This is simply not true, and it perpetuates a “if you have trouble with it then you are just weak” perspective.
While this makes sense to let the bike move underneath you while stationary (so to speak), it doesn’t mimic the power contributions of outdoor upper body. When outdoors, the tire contact patch moves laterally relative to a rider’s center of gravity, allowing a very small amount of “pivot” that can be a point of power transfer. I think of it as similar to sprinters moving the bike laterally to gain torque but on a smaller scale. Indoors with the methods you mentioned, the movement at the contact patch relative to the rider serves to just absorb the motion, leading to instability. I’ve spent many hours indoors and outdoors wondering about this, and I think the TR podcast statements about “just get a fan” are more personal than they are generalizable.
I’m sure there are some contraptions out there that more closely mimic the dynamics than others, but the vast majority of users are on “regular” indoor trainers