barge, with respect,
niche implies nothing about defensibility.
Indeed, focus on the ecology definition from below, and consider a frequent consequence of niche exclusion or collapse. A word frequented in such circumstances is "extinction". The word one uses is business is something like "bankruptcy".
Indeed, if niche implies anything it implies limited, specialised and hence vulnerable.
My statements have been both consistent and within the meaning of the words. You, my friend, are digging a wee bit of a hole.
Regards,
Dig Space.
niche ( P ) Pronunciation Key (nch, nsh)
n.
A recess in a wall, as for holding a statue or urn.
A cranny, hollow, or crevice, as in rock.
A situation or activity specially suited to a person's interests, abilities, or nature: found her niche in life.
A special area of demand for a product or service: “One niche that is approaching mass-market proportions is held by regional magazines” (Brad Edmondson).
Ecology.
The function or position of an organism or population within an ecological community.
The particular area within a habitat occupied by an organism.
The above content is my opinion.