Just to complement other's responses, accessibility is a spectrum.
We ought to believe someone chooses to use an icon for aesthetics AND usability reasons. If the icon can't be rendered at all, it defeats it's purpose despite it having a "description".
Ultimately, if a well designed, user-friendly system doesn't work the way it's intended to, it is an accessibility issue of some degree. Albeit, some times more trivial than others.
We ought to believe someone chooses to use an icon for aesthetics AND usability reasons. If the icon can't be rendered at all, it defeats it's purpose despite it having a "description".
Ultimately, if a well designed, user-friendly system doesn't work the way it's intended to, it is an accessibility issue of some degree. Albeit, some times more trivial than others.