When language professionals don't know the grammar

How well do language professionals know and understand grammar? How well could we perform what we expect of our students? I've often chafed under the grammatical accuracy criteria given to assess oral English ability. How many of you have seen criteria that, if strictly enforced, even native, educated English speakers would be penalized?

Now what if even the professionals don't know the grammar they're supposed to teach?

In the article  Cutting to the Common Core: Decoding Complex Text, Rebecca Blum-Martínez attempts to demonstrate differing language complexity by breaking down the grammar in two texts. Unfortunately, I believe she has not done this decoding well. Below I will show the examples texts, quote Blum-Martínez's explanation (in red) and then provide my take.

In this first example, we can see two compound sentences joined by the conjunction “and.” All three sentences are in the simple past tense, and the only more “complex” tense is the “would read” in the conditional past. (Blum-Martínez)

Here's what I see: The first sentence is not a compound sentence; it is a simple sentence with a compound predicate, no different in essence from "John ate and drank". The second sentence is likewise a simple sentence with a compound predicate, but the "complex" would read should probably also be simply read so as to maintain parallelism. Of course, if a compound sentence is desired, the first and second sentences could be joined by replacing the period with a comma; it is generally poor practice to begin a sentence with but unless it is being used for emphasis.

As in the previous example, there are three sentences. However, the third sentence consists of two clauses, with each clause containing several phrases that provide us with additional information (lexical density). In the first sentences [sic], the adjective phrase “less than a year” provides us with information about the length of Lincoln’s education, and thus adds to the sense of time in this “past tense” paragraph. ...And we find two different uses of “so.” In the first usage, “so” functions as an additional adverb that adds the scarcity of paper to that of books. In the second usage, “so” functions as a linking adverbial of result or inference that signals that the second unit, “he could use it again,” is the result of the former, “cleaned the board.” Thus, “so” changes its meaning because its function has changed. (Blum-Martínez)

Here's what I see: In the first sentence, I'm not sure that the whole phrase less than a year is an adjective clause as I believe a year to be an object (head noun) in this case. However, I'm not positive about that. The last sentence does, indeed, consist of two clauses, but perhaps not as in the way Blum-Martínez thinks. If she means that and separates two clauses, she would be wrong. In fact, the second so (which is really so that) is a subordinate conjunction that connects the first clause " He worked... and cleaned...knife" with the second clause "he could use it again." If I am not mistaken, in order for so to be a linking abverb(ial), is would have to take the meaning of therefore.

This should highlight a very significant problem: language professionals who themselves do not know "correct" forms. How can we teach what we ourselves do not know?

In any case, Blum-Martínez and I cannot both be correct, though we might both be wrong. Do you see problems that I've missed or mistakes that I've made?