The ENBF at https://www.w3.org/TR/2018/CR-SVG2-20181004/paths.html#PathDataBNF says:

    coordinate::= sign? number

    sign::= "+"|"-"
    number ::= ([0-9])+

This, of course, makes floating-point numbers illegal.  Surely that's
unintentional?  One assumes that scientific notation was meant to be
permitted, as well.