But it appears not to be true; Royalty Trusts (e.g. http://finance.google.com/finance?q=pbt) list very few executive officers.

Edit

And here's a non-Royalty Trust with fewer executive offices than Sun Hydraulics:

http://finance.google.com/finance?q=AMEX:SOC

But it does seem that they have fewer executives than any operating company of a similar size.