I'm asking merely about the first reason below that I colored in grey. How's "allophonic" "clearly not meant here", in the context of shallow orthographic depth?
9.7 Orthographic Depth: Two Examples
In this section and the next, we will compare two somewhat different orthographies, both using the Roman alphabet: Finnish and Scots Gaelic. The two systems differ rather strongly in what is known as orthographic depth. Finnish writing is shallow, Scots Gaelic is deep. By orthographic depth, we are talking about the relationship of writing and language. (You may at this point need to review phonemic and morphophonemic levels in Appendix A on linguistic concepts.) In a writing system which is orthographically shallow, graphemes represent phonemes; in a writing system which is orthographically deep, graphemes represent morphophonemes. Languages are often inconsistent in that they may represent some things at one level and other things at another or at an intermediary level. One commonly sees the term 'phonetic' used to mean shallow, as in 'Finnish writing is phonetic'. This is a poor choice of words on two grounds.
First, in linguistics, 'phonetic' implies subphonemic, allophonic, which is clearly not meant here.
Second, 'phonetic' suggests an absolute type of relationship between the writing system and language, whereas 'deep' suggests one end of a continuum, a much more realistic appraisal, in my opinion.[Strikethrough mine].
Henry Rogers, Writing Systems (2004), p 177.