No. Owning shares confers no immigration status or work permission. Each person's position is assessed on their own facts, and a qualifying E spouse's work authorization comes from status, not ownership.
Shares are not permission
Hypothetical example: Family purchases frequently blur two separate ideas: who owns the business and who may work in it. Ownership is a commercial fact recorded in the share register. Permission to work in the United States is an immigration fact belonging to each individual.
A relative holding twenty per cent of the enterprise has no right to be present or employed there by virtue of that holding. Within the principal applicant's household the position differs: a qualifying E spouse is employment-authorized incident to status and may work inside or outside the enterprise, while dependent children may study but may not work. A Cavan Monaghan family structuring a purchase should therefore decide separately, for each person, what they will own and what they intend to do, and should assess the second question on its own requirements.