The CAAD8 has a short wheel base racing geometry. This means responsive (twitchy) steering and an aggressive posture. I can see where that might be unsettling to some riders.
I can see that, but I don't see how a bike that he rides OK around home suddenly feels unsafe on a supported tour. I guess he might be planning to carry a bunch of gear even though the tour is supported. Perhaps it is the extra weight.
I generally feel safer with a more responsive bike, but I guess not everyone feels that way.
I can see where that would be fine and then rider ages out of that being fine. I can also see where that would be fine for club and event rides but not I am going to cover 75 miles a day for the next 12 weeks.
Aging out? Maybe. We don't know the OPs age, but I have seen no sign of aging out in myself at almost 65. In 10 years, maybe?
My thought was always that on a long tour is when I am most likely to be fully acclimated to the bike and most appreciate the more efficient posture. Again, YMMV.
I think the bigger question is why the LHT will not do for a tour.
Everyone is different, to me the LHT is more of a tank than I would want even for heavy touring. I'd rule it out entirely for me. On the other hand for someone who feels uncomfortable and unsafe on a road bike, I'd think the LHT might make sense.