What your seeing isn’t really sludge persay.
It is the result of condesation in the oil and can easily be removed by driving the vehicle for a time, allowing the engine oil to remain hot enough to ” dry out ” the condensation.
What your seeing is fairly common, especially during the winter and short, around town trips.
True sludge is a thick,black goo that deposits all around the engine internally, that usually happens when oil changes are not done on a regular basis at recommended mileage intervals.
There were usually 2 oil fill requirements.
One is without a replacement oil filter
One with a new filter.
Which is why after doing an oil change you check the level, run the engine for a few minutes and check for any leaks, shut it off and let it sit for a few minutes and recheck th oil level.
Diffence between them could be between 1/3 and 1 quart ( depending on the size of the oil filter. )
If the warning light never came on it meant that the pressure sensor saw enough oil pressure, so I doubt there was any wear due to it.