The distinction isn't universal and is often made by people from the three other Atlantic provinces.
The name "the Maritime Provinces" predates Newfoundland joining Canada, so most people from Prince Edward Island (like myself), New Brunswick, or Nova Scotia will draw a distinction between Maritime provinces (which do not include Newfoundland) and the Atlantic Provinces (which do include Newfoundland).
Most people will not even bat an eye if you call Newfoundland a Maritime Province unless they're from another Maritime province.
The distinction isn't universal and is often made by people from the three other Atlantic provinces.
The name "the Maritime Provinces" predates Newfoundland joining Canada, so most people from Prince Edward Island (like myself), New Brunswick, or Nova Scotia will draw a distinction between Maritime provinces (which do not include Newfoundland) and the Atlantic Provinces (which do include Newfoundland).
Most people will not even bat an eye if you call Newfoundland a Maritime Province unless they're from another Maritime province.