Is FIPS 140-2's "Continuous random number generator test" practical?
This requirement is a part of the general "continuous tests", and as such it's primary purpose is to detect "flatline" failures (if you can torture that analogy into making sense). Remember that FIPS-140 was originally written with hardware implementations in mind, so the approaches they take for testing sometimes seem odd for software since hardware failures tend to be different from software failures.

I don't think there's a problem, though. You could choose $n = 16$ and potentially have statistical problems, but you don't have to pick something that small. Build your construction to output the size block that you want it to. Eg, modern constructions like CTR_DRBG from SP800-90 output 16 bytes at a time, which is well outside statistical concern.

Also, you're probably not certifying a TRNG, since there are no non-deterministic RNGs that can be certified.