The issue of spiked feet on a tripod does apply for any tripod, including both old and new Gitzo's to a point. I see two special issues with the new Gitzo design for travel, both of which are really problems of the travel photographer, but problems nevertheless, which I'll speak to below. (By the way, I really like the new design.)
Taking tripods with spiked feet on them, is taking a major chance at having the tripod be rejected by TSA, and other airport security agents in other countries.
I'm guessing from anecdotal evidence that they are rejected about 50% of the time. If the spike feet are noticed by TSA or security in other countries, they will very likely reject the tripod. They aren't noticed all the time. TSA is incredibly inconsistent, so sometimes it does get through, but the consequences of rejection, in my opinion, aren't worth it.
If rejected, the tripod, if it's to go with the traveler, must be somehow checked-in. So, at that point, presumably, one's checked-in suitcase is already checked-in, so the tripod can't be put in it. That means the traveler must either get a box at the airport, if available, to put the tripod in, to conceal and protected it, before checking it in, or must just check it in "naked," Either way, that's not a prospect I'd like to face.
As to the special problems created by the new Gitzo spiked feet design, first, as the spikes are hidden under a rubber outer casing, some photographers might be inclined to think TSA or other airport security agents in other countries probably won't notice the spiked feet, but they will show up clearly in carry-on x-ray. An alert agent will see them and most likely say you can't take the tripod into the cabin.
Second, I think that unless the photographer uses the spiked feet regularly, with the spiked feet out of sight, they might forget they're there and get caught at the airport when TSA reminds them they can't take a tripod with spiked feet into the cabin. That kind of happened to me a few years ago when I took a Manfrotto tripod in my carry-on, which had retractable spiked feet. I hadn't used the spikes in quite a while and forgot about them. They were noticed in x-ray and I had to check the tripod through to my destination. Fortunately, I was able to secure a box at the airport in a shipping store there, and it was undamaged when retrieved at baggage claim.
When I'm taking a tripod with me when I fly, and I have no checked luggage, I alway put my tripod in my carry-on, and I make it a practice to remove the spiked feet from any tripod I'm taking in my carry-on. In that case, if I want the spiked feet with me, they are put in a bag in my carry-on. I haven't been rejected from doing this in many years.
If I have checked luggage, the tripod goes in my checked luggage, and it's never been rejected in my checked luggage. To me that's the safest way to do it. For most of my travel, when I take a tripod with me, I have checked luggage, because of the length of my trips, and my needs on the trips.