While Nehan Conversion upgrade is researching, if you hover over a Buddhist monk’s conversion ability, you will see that it is called “Nehan Conversion” even though it hasn’t finished researching yet. If you cast it, you won’t get the speed buff, however you will get the reduced 90 second cooldown buff (again, this is while the upgrade hasn’t finished researching). Moreover, if you were to cancel the Nehan Conversion upgrade while the conversion cooldown was running, the cooldown gets reset instantly as it reverts back to the normal Buddhist Conversion. This lets you basically get a 2nd conversion with no cooldown with the same monk.
(you can see the Nehan Conversion tooltip while it is still researching)