That is a replaceable seal surface. Normally not replaced until the wheel bearing seal has damaged it and it will have a groove in it where the seal touches it.
95% of cars have that built in and when it's damaged you have to replace the strut/knuckle/spindle.
A replaceable seal surface ring is common on industrial equipment and large trucks (think Semis here).
I prefer a removable ring. It's the engineer's choice.
A non-replaceable ring is an accountant's choice.
914/4 had the non-removable ring.
914/6-911 had the removable ring.
Note: if you change the seal at normal maintenance intervals you will not damage either design.
Preventative maintenance is the key here.
Final couple tips, sometimes a micro sleeve is available to repair a damaged integral ring. This is a super hard super thin cylinder that fits tightly over the original shaft, and I've never seen one of those get damaged by a seal. Commonly used for crankshaft front or rear seals but it's worth looking for if you have a problem with any damaged seal surface. You search for this by diameter only. Lots of different sizes are available.
On replaceable sleeves I use a sleeve retainer compound. I haven't done a Porsche sleeve yet but something like this is what I use for trucks/industrial equipment.
https://www.amazon.com/Permatex-64000-Tempe...69631&psc=1