I've stayed off this thread, which is extremely divisive (in itself, that is not without interest in what it says about people's relation to a monarch).
But that's potentially a useful distinction. Mourning is perhaps the outward, ceremonial expression of grieving, with certain rites attached to it. I suspect that
@twosips (a thoughtful lad, by the way, not for one second someone I'd consider wilfully provocative, to judge by his Youtube thing) would argue that neither are being done or experienced by the whole nation, and that's his whole problem with that narrative. Which, let's be honest, has been pumped out 24/7 since her death.
If I've understood him rightly, his objection would not at all be to people grieving, or even mourning, their queen. It's that we're being told that everyone's in that state of mind and expression, when they're palpably not.
And if the distinction holds good, that there's a sort of coercive mourning going on, which doesn't correspond to inner grieving.
But I may be overthinking it.