Employing more formal language in technical writing is like matching the tool to the job. You could cut down a tree with the saw blade inside a pocketknife, but you would be better served using a chainsaw for that job.
Likewise, more effective technical writing has certain characteristics that make it more effective. One such characteristic is a tone with greater formality than we typically use when speaking. Hence the importance of understanding the differences between spoken and written English. More effective technical writers avoid colloquialisms.
Inside of, which we discussed two posts ago, is one such colloquialism. Bunch is another colloquialism under certain circumstances. A bunch is literally a number of things growing or fastened together. Using bunch in reference to things (such as several plates welded together) is appropriate because that use is consistent with its formal definition.
However, bunch also has informal meanings, and when referenced these definitions makes its use colloquial. Using bunch to mean a group of people or a lot of something may find acceptance in speaking, but such informality produces less effective technical writing.
Consider the example sentence in the cropped graphic above. Exactly what does the writer mean to say? Is the intended message about the quantity of inspectors on site? Or is the intended message about the group nature of the inspectors? Whatever the answer, the writer should employ more precise language to convey the intended meaning.
At that point, a group of inspectors appeared on site.