All you need to know and remember is 3 things.
1. The manufacturers stock tires are for delivery purposes only since the vast majority of RV owners choose to park their new units and use them a seasonal cottages
2. Because of fact #1 the manufacturers stock tires will be the absolute minimum spec required and the cheapest supplier sourced tire bidder.
3. The RV transport company driver has no reason whatsoever to follow the 65 mph maximum speed rating of the vast majority of ST tires as time is money for those guys and the risk of a speeding tickets outweighs the time factor.
With these facts in hand why RV'ers who plan to tow their units rather than use them as park models don't demand optional upgraded tires at time of purchase or as a condition of purchase is beyond me.
To each their own, but in my mind towing confidence with quality tires with weight capacity to spare is priceless.
The OP is correct to be asking these important questions and hopefully will make the right decisions when it comes time for them to purchase.