default settings are merely suggestions about fit, because fit is ultimately created and controlled by the mill. no default value is "correct" by default and should not be taken as such.
every CAM philosophy is to mill a part as close to spec as possible, if possible without going over except in rare cases.
this fit accounting is so that labs can control the fit to their preference; some people want loose fit, some people want tight fit. ultimately many labs use handpieces to modify fit any any circumstance anyway, making this fit control pointless.
which is why every library produces an equal fit distance, from implant to implant. the fit is just a spec, controlled by production not by design.
of course this falls on its face when talking about implant analog to printed model. many libraries give NO fit tolerance, rendering printed model fit extremely tight.
are you having a problem with peek specifically that requires attention?