Hey xanthozylum,
welcome! And thanks for your first post!
I am not sure whether there really is a better or worse approach. As your friend indicated, 'topping-up' is quite common in ceremonial contexts (although I would be interested how this was handled in traditional, indigenous settings). I think the reasoning here is to give participants a chance for a 'smoother' and more controlled entry. And this is reasonable IMO, especially for less experienced users. And usually, the consecutive doses will have an effect (even though maybe slightly less so than when drinking everything at once due to some tolerance building up).
That said, Aya is a mystery. The same doses can be quite different in intensity on different occasions. And it can also be the case that doses don't do anything (even the initial ones) - you might just have encountered such an occasion.
I would suggest you simply experiment a bit more. If you feel that your first dose did not get you far enough, maybe increase it slightly the next time? Or have another try with consecutive doses and see whether your experience will be different.
As I mentioned, I do not think that there is a right or wrong approach. But for what its worth, I personally tend to not redose too much as I feel that taking a psychedelic initiates some kind of 'journey' or 'narrative'. And I tend to try to just let that journey unfold, as opposed to altering it via another dose. Now the exception here is when taking caapi/rue and potentiating this with (separate, vaped) dmt doses. I enjoy doing this as I feel it leaves the caapi 'journey' intact, while just lighting it up again a bit more.