In fact, open source means free support, in the sense that independent and libre support can form around such a product. This may not be free of charge, if that is what is meant.
"Means" and "can" are incompatible. Either free software may mean free support, or independent and libre support always forms around free software projects.
Source: I used to make a living offering independent support for commercial software that someone else made and sold.
I was fortunate enough once that a big company used an algo I wrote and contributed a performance improvement in an area I'd had writers block on, but that was the exception.