If they mean "only a small subset of your users need accessibility support" this might be true, but I haven't worked for a organization selling software in the past 20+ years that hasn't needed to provide support, and those orgs are the audience for a .net cross-platform UI solution, so in that case they are wrong; almost everyone "needs accessibility support".
replyprovide support on a product and accessibility are really different things.
replyaccessibility is like implementing braille and things for deaf and colourblind etc.
support is resetting password and helping with accounts etc.
so one is to get a certain category of users to be able to access your site in the general sense. the other (support) is about helping people who already can access your site or service.