Acidified infusion, and why it is a procedure
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What the method actually is
Penn State Extension describes soaking the herbs or garlic in a 3 percent citric acid solution before use: roughly two-thirds of a cup of coarsely chopped garlic cloves, or about a cup and a half of herbs, to two cups of the solution, left for at least 24 hours and then drained before the oil goes anywhere near it.
Why the ratio and the time are the control
The acid has to reach the inside of the material, not coat the outside of it, and that takes contact time and enough solution to stay acidic while it works. A shorter soak, a smaller volume of solution or a coarser preparation each weaken the control in a way nothing downstream recovers. This is the reason it has to be written as a procedure with numbers in it rather than described as acidifying the garlic.
Acid in the oil does not do the same job
Adding acid to the oil afterwards is a different thing entirely. Acid and oil do not mix, so the acid does not reach the inside of a clove sitting in the bottle. The sequence is the point: solution first, drain, then oil.
This is published home guidance, not a filed process
Extension guidance is written for home preservation. A product you intend to sell needs a process established for it by somebody qualified to do that, and the method above is the starting point for that conversation rather than the end of it. Build the documentation as though it will be read by somebody who was not there.
Record every batch against the method
Which solution, which ratio, when it started, when it was drained, who did it. A safety control you cannot show you applied is in the same position as one you did not apply, and that is the position a complaint finds you in months later.