Hi, amazing, congrats... rooting jaboticabas is possible, there are a lot of documents on the net, but it is very difficult and it varies with species, dont know what is your species (not m cauliflora, maybe m. jaboticaba -sabara...).
The best time to do it is spring and the best is to use new growth, as you did! Jaboticaba is very hardy and a cutting could survive in water for many weeks, but, normally, they dont produce roots! and there are documents on the net that show you that rooting hormone would not help. But maybe you species, temperature and rooting hormone were the best possible to root it.
I could never did it (tried with 10 cm new growth cuttings from myrciaria cauliflora - paulista), will try the next spring.