What the video discussed was efficiency, and it's been known for a while that clipless pedals do not increase pedaling efficiency. But it's a bit reductive to claim that no benefit has been demonstrated just because there's no difference in efficiency.

There are other benefits to clipless pedals.

1) Foot pressure mitigation. Most longer distance tourists become fairly strong riders at some point or another. That means they'll be able to put out a fair deal of watts and thus pressure against the pedal, which, with shoes that are too soft, can cause discomfort or pain over hours of riding per day. The only shoes that remove the pedal shape feeling with my typical pedaling forces are heavy duty hiking boots, which are frankly pretty bad for riding. All of my cycling shoes however are stiff enough that I don't feel the SPD-cleat or pedal even when doing max efforts.

2) foot placement. For me it gets really old really fast when my foot is in a different spot on the pedal all the time, especially on multi hour rides. With clipless I simply don't think about my foot placement. My foot is where it's supposed to be and won't shift, except for float rotation. Having less bike fit related things to think about is a benefit in my book.

2.1) Leg health. Assuming the cleats have been adjusted properly and the bike has been fit correctly, clipless pedals likely prevent overuse injuries over flat pedals. A hot take I know but clipless pedals with sufficient float reduce variables and let the foot/leg stay more relaxed when riding.

3) Foot retention. I've found myself in situation where I've gotten in too steep too fast with too large a gear and have to tear myself up the hill whilst pushing and pulling the pedals and wrestling the bike. That wouldn't happen without clipless and I'd have to walk-a-bike. Also when riding over rough bumpy terrain or simply riding really fast it's nice to know your feet won't come off the pedals and cause you to crash.

I'm sure there are other benefits as well but these were the ones off the top of my head.

As for walkability, all the SPD shoes I've tried have been plenty walkable. Would I want to do multi hour hikes in them? Well, not in all of them. In some maybe I would... But all of them have been more than good enough for the walking one typically does on a bike tour. Then again it's not something I really have to think about. I just walk in them. My current touring shoes (Lake LXSDL) are pretty great allrounders.

As has been discussed, mounting/dismounting seems to be a matter of preference. For me the quickest way to get a foot off a pedal is with SPD's as opposed to flat pedals or other pedal systems, since with a quick twist the foot just sorta flies off the pedal and to the side. At this point if's reflex since I've been mountain biking with SPD's for a long time now. Mounting and setting off could potentially be quicker/easier with flat pedals but that's one of the reasons why my touring bike has dual sided pedals. When I set off I either push at the flat side and clip in when I'm moving with enough speed or I clip in immediately. Luck of the draw really.