https://en.wikipedia.org/wiki/Strike_action
"Strike action, also called labor strike, labour strike and industrial action in British English, or simply strike, is a work stoppage caused by the mass refusal of employees to work. A strike usually takes place in response to employee grievances."
https://en.wikipedia.org/wiki/Boycott
"A boycott is an act of nonviolent, voluntary abstention from a product, person, organization, or country as an expression of protest."
https://www.dictionary.com/e/strike-vs-boycott/
"The key to remembering the difference between boycott and strike is to figure out who is taking action: the consumer or the employee? Workers strike against their employers while consumers opt against financially or physically supporting something as a way of peacefully protesting against it. Consumers boycott."
Healers do not benefit from their own fulfillment of the Healing Slot in a queue, they provide it. In this analogy, Healers are "workers", not "consumers", and the "employer" is SE/CBU3, providing design-incentives for Healers to exchange their time for other benefits (such as EXP, Tomestones or, hypothetically, "fun").
Non-Healer Players "consume" the benefits provided by Healers.
If other Roles refused to group with Healers, that would be a "Healer Boycott".