I saw it reported on experian 2 days after I got approved. Are you suggesting barclays reported to experian immediately but waited a month to report to TU?
1. Just because the card was reported, doesn't mean the balance was reported.
2. Even if the balance was reported, it didn't necessarily change your score.
3. Even though your balance changed every day, it won't update more that once a month.
4. Finally, TU is certainly much slower to update than EX. Much much slower. (I don't know if it's because everyone reports to them last, or it takes them the longest to update the info, but this is how it is)