Using Select > Same > Fill & stroke, Select > Same > Fill color, Select > Same > Stroke color, or Select > Same > Stroke weight on any item in an Illustrator document also selects all empty text boxes, regardless of actual fill or stroke. I would like to keep the text boxes as placeholders, as I'm using the document as a template for designs where a variable number of boxes are used.
I'm using Illustrator 27.8.1; I observed the same issue in the previous version but can't speak to older ones. I've reproduced this in multiple documents. The issue does not occur with the other Select > Same functions (like blending mode, opacity, etc).