It may be an unnecessary feature, but isn't raising the tag axle a required part of the slide extension protocol? I'm not sure because I don't have Prevost slides. While I probably could back into my garage without raising the tag, doing so makes it a simple 2 point turn instead of a 4 or 6 point. The manual also goes on to say not to lift the coach without the tag raised or you may suffer suspension damage; I'm assuming there's a risk of tag axle over extension if left aired up. Lastly, the warning to come to a complete stop before lowering the tag doesn't really apply to heavy motorhomes does it? In our case the tag is never truly lifted so the tag tires are always spinning eliminating the sudden spin-up when lowering the tag.
I'm a believer in the reduced turning radius and I often take advantage of that - my wife has a penchant for booking us in old KOA's! I would truly be unhappy if I lost this feature. I don't think the additional load is an issue if speeds are low and durations are short. During cruise speed driving, the dynamic air pressures in our air springs surely exceed 120 psi on a routine basis and the tires and axles can easily handle those loads. I believe design allowables are in the 3 to 5g range in the upward direction.