coerce and 'number' typed options

I have an option definition like this:

	'timestamp': {
		description: 'Timestamp to use (ISO 8601 formats)',
		type: 'number',
		coerce(value: any) {
			const ts = moment(value, moment.ISO_8601, true);
			if (!ts.isValid()) {
				process.exitCode = 1;
				throw new Error(`Cannot parse provided timestamp ${value}`);
			}
			return ts.valueOf();
		},
	},

Somehow this started to break "recently", and complains about the value inside coerce being NaN, when the value provided to the option is something like this: 2021-01-21 17:25:47.
ISTR that this used to work in processing the value correctly, but looking at the sources I see that yargs-parser's processValue is executed before applyCoercions.

Now, I can get the behavior I need by changing the type to string, but before doing that: Is this "intentional", i.e. is the type intended to mean "type before it gets to coerce", rather than "type after it has been coerced?"

Start by reproducing the timestamp option with type set to "number" and inspect yargs-parser's processValue and applyCoercions flow, as identified in the issue. Determine whether coercion should receive the original value or the pre-parsed value, then document or correct the behavior so the intended type and coercion contract is explicit and verified.