That's a surprising link! Thanks for that. You live and learn.
I can see their point, but it does rather depend on WHERE you board it out. Boarding 50% of it means that it's going to be either down the middle or up one end anyway, which is going to put a localised stress on the joists, doing as much as you can reach and using proper loft boards fixed to the joists spreads the load, as long as you're not tempted to go silly with the new-found space.
As my reply infers, I've yet to meet
any BCO who, as you've discovered, gives a toss either way if you're not going to LIVE up there.
And, as you say, what they don't know won't hurt them.