I think this is misleading. They're offering to match your Chrome extension with an equivalent Firefox extension. But they are not providing an extension compatibility layer to run Chrome extensions.
And whether this is using equivalents or a compatibility layer, to the average non tech savvy person is irrelevant. They don't care as long as it's the extension they had and it works.
Currently the only browser (I know) that has the compatibility layer is the Orion browser by Kagi search engine. It is based on WebKit but expose API for both Firefox and Chromium extensions.
Not total compatibility but FF web extension compatibility is higher in number than Chromium.
I don't. If they meant that they would've said it. I had no moment of misunderstanding at all. Of course it would mean "I'll automatically match to the equivalent one so you don't have to do it manually". They just wanted to state it in a way it was easier to understand