I feel like an issue with that is if the tree is old enough to have flowers, fruit is only a year or so off at most (maybe you don't let it set fruit the first time it flowers) and then you can just try the fruit. If all you need is a leaf smell, the iteration time is a lot faster - don't need to wait for flowers.
My thought was to graft the saplings onto a mature tree to hasten maturity, which should get me to flowers sooner.
I have noticed that flowers when broken up have uniquely identifiable aroma characteristics, but only after they open as female. The aroma intensifies by male stage, but outside the active bloom period, I haven't been able to tell them apart by smell.
So I don't think that they have a sap component like mango unfortunately.
If I only have a limited space on adult rootstocks, that limits the selection process a bit, so I was thinking to speed up the selection any amount since they are so easy to graft when active.