They don't have to support an operating system if they don't want to - it's up the customer demand, really, for them to justify expending resources to support an operating system. If they don't want to spend money on supporting it, it's a decision that they make, but it doesn't reflect their understanding of open source nor does it mean that they are not for open source.

After all, why should they support an operating system just because it is open source, even if they "get" open source and support the philosophy of open source?