While I don't profess to be an expert on tires by any stretch of the imagination, a great many post have been made on this forum and other forums around the net on the virtues (or lack thereof) of different brands/originating countries/manufacturers of tires... with that being said, from my reading and investigations, if you are going to exchange a brand of tire you don't trust for one that you can and you are needing an "E" load rating, Michelin XPS Ribs seem to come to top a lot... expensive but some say they are worth it... if you are looking for "G" rated tires, the market narrows to either staying with foreign brands for GY 614s..
As far as LTs are concerned, my current Cedar Creek has 235/85/16 LT E rated Merits (stamped "Made in America" for whats that worth) but they are pushing 3 years old now and will be replaced if I have to haul it a long distance before I get my Landmark... as I have looked at dozens and dozens of 5th Wheels RV at all price levels in the last few months/years, there seems to a predominance of LT tires as STs are harder and harder to find in 16-17-17.5" tires.. when you get into the E and G ratings (minimum of 10ply) and get an "up brand", the sidewalls are quite stiff, therefore negating the need for STs...
As far as what kind of tire Heartland puts on... that is a roll of the dice, but I agree they won't put a tire on that is dangerous to the end-user (albeit not to our personal preferences and not withstanding all the horror stories of the "china-bombs"), but nothing stops you from replacing them immediately upon delivery or negotiating with your dealer for a swap for the tire brand you wish..
Again, this all just my opinion and your mileage may vary...