Yeah, seems stupid but you need to cut the opening.
I used Dremel on mine. In Russia we all buy this cap from a guy who makes it on a 3D Printer (around 8$
). And there are a dozen of filters that fits perfectly (but GM OEM 52485513)
BTW, GM in not unique in this crazy doing. My 00'Subaru Forester had almost same situation. BUT it has an opening and a cap, but no filter inside and it is even not available in parts catalogs (refer to all 1Gen. Foresters from Japan Domestic Market). Of course it was not a big problem to choose something that fits in a place- BUT yes, some car makers do this. What is the reason? Do not know, may be they think our modern roads are already dust free environment? Who knows