A reductive process is a process where you take many ideas and boil them down to fewer ideas. The opposite would be something like a brainstorm, where you try to get more ideas.
And I don't really think you actually have no idea what "product definition" may mean. :)
In your interpretation, a proposal of a value one attempts to deliver is a process wherein one takes many ideas, and boils them down to fewer ideas.
That is not what the meaning of the term “proposal” is; no one uses it to mean a process wherein many ideas are reduced to fewer. A proposal is simply stating one's plans, not a discourse.
> And I don't really think you actually have no idea what "product definition" may mean. :)
I normally have an idea, but not in this context, as it speaks of stages of a product definition. A definition does not have “stages”
It's really difficult to understand your confusion here. "Definition" is referring the the act of defining, not the formal statement that results from that process. Are you reading it as the latter?
Every product I have ever worked on had definition stages. How else does the formal definition come into being?
Having said that, this kind of syndoche where a process is described by its output doesn't seem particularly unusual or UX-specific. When a coworker says it'll take an hour to do requirements I know what they mean.
I'm not sure why you think "definition" (1: the act of defining https://www.dictionary.com/browse/definition) cannot have stages.
So essentially, your interpretation can be reduced to the advice “It is best to think about what one's product is, and whom it targets, before one makes a proposal about it.”?
If that be your interpretation, then that certainly does not follow from the text, and is contradictory with the interpretations others have given.
The focus on communication and discourse is paramount, because UX brings the user to the forefront and then has to convince owners and implementers. This kind of convincing is important and often challenging, because there are often tradeoffs involved.