> Text is a coherent and cohesive group of one or more sentences
That would be prose¹ (and to some degree poetry).
Text² is an object that can be read. And by that definition…
> A logo is not text
… yes, a logo can be text.
----
1: https://en.wikipedia.org/wiki/Prose 2: https://en.wikipedia.org/wiki/Text_(literary_theory)
The purpose of text is to convey information, ambiguously or not. Text is a coherent and cohesive group of one or more sentences. A logo is not text, it is a graphic that represents an establishment or a brand. It may include some text, but it is as text as a photo of a road sign with some text on it is.