Our Canonical JSON implementation precedes some standardization efforts, and our float representation differs from the most polished one (the only one with proper spec, tests suite, and reference implementation in Go).
If no float has ever been published among the Remote Settings data, then we're good. If there are floats (or were recently), then we should investigate with data authors if their data could hit one of the divergences (namely scientific notation with exponents), and/or if there is a migration path.
But for now, if we forbid them (ie. server returns HTTP 400), then we make sure that the problem does not get worse. For new use-cases, floats can be transported as string (or integer + denominator)