Roland Perry wrote:

But what if I were to organise a meeting, booking a conference room,
greeting guests and holding a seminar (where I was speaking). Is that
closer to "work" than "business"?

I manage engineering teams in the US, India and the EU and I can say the rules
aren't black in white. They strongly depend on your visa legal counsel and the
mood of the border control agent on any given day.

In general, the rule of thumb I use is that talking in any format (one to one,
giving or receiving instruction to one or many people, etc.) falls under a
business visa.

Pick up a screwdriver, connect a cable, even in the context of training and
things start to get complicated.

There are also ancillary rules - your paycheck needs to come from your home
country, your reporting manager needs to be in your home country and you are not
allowed to take direction from any local person.