I think you're right.
My son had some 'gum' stuff in his new tyres on the recommendation of the garage that fitted them. When he took the bike for a MOT test they spotted a nail in the rear tyre and said they couldn't repair it because of the 'gum' - couldn't get a patch to stick. He had to buy a new tyre. When he had a flat 2 weeks and 300 miles later, I took him out a seal and inflate kit that I kept in my car and it said 'proceed with care etc until you have the tyre properly and permanantly repaired'. You've guessed it, when they took the tyre off they said they coudn't repair it so he had to buy another tyre. Sounds like tubes are the way to go !
