It's real nice to see you guys having better luck than me. I will keep trying. Which I am anyway, but success is not every time for me.

Sealant is compounded for tubeless tires. The sealant is supposed to flow together with escaping air. It is just one layer of tire on a tubeless. With a tubular the air leaks out of the tube and then there is a casing. So the flow is slowed and somewhat redirected. Yes, it works. It does not work so well or so reliably as with tubeless.

Modern tubulars are plain heavier than 60s 70s 80s 90s tires. The casing is not so limp. Remember when folding the tire under the saddle it would be flat sections of tire that just folded with no resistance? Modern tires much stouter. The venerable Jandd tire bag has not changed at all, it now carries one tubular rather than two.

Vittoria Corsa is latex tube. The heavier casing slows air loss compared to an old Clement.

Sealant eventually dries out. Tubeless riders get busy and scrape the gunk out, put in fresh. With butyl tubes and very darn little air movement, 100% humidity in there, it should stay wet a long time. Latex tubes with sealant in tubulars I've found it bone dry after four months. Yes, you can add more. Start to lose the tubular feel as the weight adds up. To avoid this problem ride more miles and wear out those tires.