Please tell me if this is correct.

On some of the OEM air cleaners there was a small plastic fitting with a filter built in, you obviously don't have that on that aftermarket air cleaner. That would catch the little bit of oil and any debris flowing though there.

Secondly, if you find the time, it might help to pull the valve cover and see if there is a baffle under that breather, if not, the oil can overload the filter in that breather cap and flow through to the air cleaner.

This isn't a major issue, nothing a little tinkering won't correct.