A hack writer is a term that massively pre-dates the usage of the word hack in technology, often used to describe journalists or pulp novelists, so I would assume that it is a deliberate play on words marrying more than one meaning of hack.
Which would also mean that the term "hacking text" in this context is itself a bit of a hack.
...
edit - I went for a look at old uses of the word hack as it pertains to writing and found that there is another variation in meaning, that of "hack words".
Here it is in use from the 1858 periodical, "The Ladies' Companion", in a passage that as chance would have it is discussing the creative usage of words -
"Of the influence which German literature Jean Paul and others has had on Carlyle enough has been said elsewhere. This influence certainly shows itself markedly in his style though by no means detracting from its originality.
It has given to him a somewhat burdensome richness of compound words and a few unfamiliar derivations. He is fond of seizing upon the primary meaning of a word and bringing out that meaning forcibly by contrast and repetition. He introduces innovations of foreign words to a great extent and not unfrequently uses simple ones in an obsolete or new sense.
These may be looked upon as faults but it will be found that his foreign introductions are mostly from languages which form the basis of English having an affinity to accepted English words and that they invariably have a peculiar significance which could not have been given by more common expressions. His obsolete or new senses too show generally an evident reason for their adoption.
He is fond of hack words - a kind of slang of the day; for instance, "sham", "jargon", "gigmanity". He uses such words as watchwords of the time wherein he writes, as bearing in them a nineteenth century view of things."
