Yes! it is correct. If an infant or adult (of any faith) is baptized and immediately dies after being baptized, they go straight to Heaven because their soul is pure as can be.
Although we cannot say for certain, I'm sure there are many saints through history who have died in 100 percent purity, though in this culture it is hard to imagine it.
Once a baptized person reaches the age of reason, they would be culpable for any sins they knowingly committed and be responsible for confessing them and making proper satisfaction or penance for them.
I hope this helps,