It depends on whether this source is using the strict dictionary definition of "quantitative", or some field-specific usage with a nuanced meaning
quantitative (adj): relating to an amount that can be measured
This is a binary, yes/no condition. Something either is quantitative or is not quantitative, with no need for comparative or superlative.
However, it may be that there is a kind of spectrum between quantitative and qualitative algorithms, and it is possible to define an algorithm that leans more towards the quantitative side of things -- ergo, one that is "more quantitative" than other algorithms.
It's the same with "perfect" and "square". Yes, as a mathematical concept, something either is square or is not square -- but in the real world, where nothing is actually square, it's fine to say some shape is "more square" than others.