> Programmable calculators manufactured by Texas Instruments, Hewlett-Packard, and others typically employ a floating-point BCD format, typically with two or three digits for the (decimal) exponent.
Then that's how they're encoding the components of the float. BCD itself is not a floating-point, it's just a different way of encoding a fixed-point or integer. If all you want to do is use floating point but expand the logarithm and mantissa then that's completely tangential to whether or not they're stored as BCD or regular binary values.
See also binary coded decimals.
https://en.wikipedia.org/wiki/Binary-coded_decimal