No, they become perfectly mild.
The pungent sulphuric spiciness is either massively diluted into the liquid or completely negated by perhaps the sugar [calories], vinegar (pH) or fermentation {which transforms compounds similarly to cooking}.
Curiously, the spiciness is all gone by the time I first try the pickle (24hrs), before the fermented taste develops.
The pickle tastes more like commercial 'pickled ginger' than radish.
The radish has the taste of the liquid, pure Sweet and Sour zing (a flavor profile kids would enjoy) - the vegetable merely provides a crunchy texture [and the microbes].
I've so many radishes that my pickles are currently 90% radish, eaten everyday - whereas eating a single raw radish daily would have me doubled over with pain. (IBS, but mainly Gastritis)
Lots of people similarly can't tolerate raw garlic (eg Aioli) but cooked garlic is fine.
Radishes sure are easy to grow and bulk seed is cheap.
Growing them transformed my small daily trickle of harvested veg into much more abundance - and its satisfying harvesting
root crops as an understorey to other food plants, while tomatoes and beans clamber over and around the whole productive mess.