The compartment there is not for the filter that comes with the bags. You'll notice the cut lines don't match up. That filter behind the bags is the pre-motor filter. It's a very wirey filter, kind of like the back of a sponge. It's not smooth.
If you try using an exhaust filter on the motor intake, it will starve the intake, stressing the motor.
My previous comment about the filters was unclear, sorry.
I just opened a fresh box of GN bags for my C1, and it came with two flat filters along with the bags.
One is a soft filter with Air Clean printed on it. It has cut lines that match the size of the HEPA filter.
My C1 came without the HEPA filter but had a filter holder designed to hold the soft filter if you don't have the HEPA. I put a HEPA filter in mine, so I don't use that holder or this soft filter.
The other is the wiry scratchy filter which goes in the vertical filter holder. This is the pre-motor filter you're talking about, and it has cut lines that match that filter holder. I use this one along with the HEPA filter.
Are we on the same page now? Want to make sure I didn't get it wrong. :-)
Interesting. Yes, when I bought my C1 there were two models I looked at with a $100 price difference. They were identical other than the more expensive one including a HEPA filter where the cheaper one had the Air Clean filter and holder. But a HEPA filter by itself only cost $55, so I bought the cheap one and a separate HEPA filter.
In case it helps, here are the bag+filter packages I've been getting:
If you try using an exhaust filter on the motor intake, it will starve the intake, stressing the motor.