Which is half true. All of them are vulnerable to Spectre. So far as I've heard only Intel (and maybe ARM) are vulnerable to Meltdown, because Meltdown exploits the lack of security checks on speculative execution that only Intel implemented. It's ambiguous if ARM is vulnerable, I've only heard people saying either "maybe" or that they haven't validated that.

Edit: Elsewhere I found a link to ARMs page where they breakdown exactly which of their processors are vulnerable to both Metldown and Spectre and it looks like quite a few of them are vulnerable to one or both of them.

I recognize the positive spin, the fact of hardware vulnerability is still little understood, and the trust placed in the cloud ecosystems is almost absolute. I'm aware that I would be planning to go on a Microsoft like security commitment and the sheer resources available to Intel if concentrated on the silicon features capable of e.g. detecting a miscreant hypervisor look like the next wave of products and marketing. To achieve this spin, however, Intel needs to day much more than they have. They can maintain their current line but score points with sceptics by demonstrating how some attacks work on Intel processors in the wild. Coordinated with Industry wide patches, making more point which is missed here how Microsoft and others patched branches in November, the wrap is to offer all customers running on vulnerable silicon migration and s performance bump. This is not a cheap process, but the political climate almost demands resolution at this level.