I am sure most could do it under the hood. They would have demonstrated that umpteen years earlier when getting their licence.
Problem is when it happens for real some time down the track and they do a rate one turn and find themselves still in the clag and in real life with no one to help. And they are at low level because they have tried to get under deteriorating conditions that looked sort of OK until a few minutes ago. And now do not know where they are in relation to the terrain. And seeing little bits of ground appearing when they do not expect it and it appears to be at an angle they do not expect while turning they get the leans. And having only ever done instrument flying under the hood, not for real, always with an instructor next to them and even then rarely and under no real pressure, they start to panic and turn to wherever they thought was better but it doesn't get better.
I still think the idea that exiting IMC by a simple 180 turn is probably not actually an option available when this situation claims VFR pilots. By the time they are onto instruments they have already dug themselves way past that. The situations that are resolved by a 180 turn I suspect never make the accident reports.