Yes. Note that OTU background information is constrained as well, and I think this is good for publishers.
In actual games, I find that noone feels particularly constrained by things not printed in the rules. Quite the opposite. The grognards already know what's been made available in nearly every edition of Traveller, and the newbies bring their own non-Traveller ideas to the table, and between the two groups some very interesting and enjoyable syntheses happen.
