Is the correct answer. As you say, as the number come down R will fluctuate with localised spikes, rising quickly before dropping away as quickly. This was demonstrated in Germany a few weeks when the media went into a frenzy when in rose to 2.8 there briefly, before quickly dropping back below 1 as has done her.
But that does not mean that the overall averaged value isn't significant.
If it goes above 1, infections will rise increasingly rapidly.
Or if you don't want to think about R, look at infection levels. If they start to consistently rise, then unless something changes that rise is going to keep on going and to accelerate.
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