When a closure must be child resistant
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The entry
"Household substances in dry forms such as granules, powder, and flakes, containing 10 percent or more by weight of free or chemically unneutralized sodium and/or potassium hydroxide, and all other household substances containing 2 percent or more by weight of free or chemically unneutralized sodium and/or potassium hydroxide."
Free or chemically unneutralized
Not the total alkali in the formula. What remains unreacted and available in the finished product. A formula with a great deal of hydroxide that is substantially neutralized can sit below the threshold, and one with less can sit above it.
Which means it is a measurement on the finished product
Calculating from the batch sheet gives you what went in. The threshold is about what is still free, so the number comes from testing what came out.
Why dry gets five times the latitude
A child can swallow a mouthful of liquid in a second. A powder is harder to ingest quickly and in quantity. The rule is reasoning about the route of exposure rather than about the chemistry, which is why the same ingredient has two thresholds.
So the format decision is a compliance decision
A formula at 5 percent free alkali needs a child resistant closure as a liquid and does not as a powder. That is a real degree of freedom and it is only available before the format is fixed.
Dry forms are listed by example
"Granules, powder, and flakes". A laundry powder and a scent booster are both squarely inside that. A paste or a gel is not obviously either, and that is a question to resolve rather than assume.
This is one entry among many
The section lists a long set of household substances. Alkali is the one this category runs into most, and a formula containing anything else on that list has to be read against its own entry.
A child resistant closure is not a safety claim
It is a packaging requirement for specified substances. It does not make the contents safe and it does not substitute for hazard labeling.