[gerdesj]

lol.

You are quite correct - that boat isn't the same as a modern one and you've spotted it. The sail is fixed fore and aft (sheets) and it looks like you move the sheets around as you need. It has a yard which we assume works like our usual square rigged vessels but it doesn't. That vessel can work upwind a bit.

Zoom in on the modern yacht in the photo. It's staysail (front triangle) is luffing slightly (laminar flow is broken). That means that the old boat is working fine at the same point of sail as the modern boat. The old boat probably doesn't have a decent keel so will slide sideways a bit.

This sort of analysis needs proper sailors involved and it looks like none were.

[simmerup]

It's too much to expect an academic to engage SMEs