Offer of a 3 blueberry plants - pollination ?

They might flower at different times - my three blueberries never flowered together (I now only have two; one died). But just because plants don't ripen fruit together, doesn't mean that they don't flower together. For example: Discovery apples ripen in August, while D'Arcy Spice apples ripen in November.
Yet in my area, both tend to flower about the same time.

But despite by blueberies not flowering together, and not apparently having many insects visit the flowers, pollination never seems to be a problem.
I reckon that blueberries are self-fertile, but that crops may be better quality or more reliable if cross-pollinated.

Many nurseries say "get a pollinator" but they don't actually say what would flower at the same time.
Perhaps it's a way for nurseries to sell us more plants; to panic us into buying two or three to ensure cross-pollination.

If blueberries were self-sterile, then even buying two or three may not ensure crops, since the self-sterility mechanism will also mean that any from the same family line would also be at least partially sterile crosses (in the same way as Cox's apple is a poor pollinator for its offspring, and its offspring are poor pollinators for it).

Another way to look at this, at least in the case of apples, is that the bloom period in spring lasts maybe 6 weeks whereas the ripening period is far longer, from July to November. Varieties can therefore overlap for flowering time without having the same ripening time. Also, as FB implies, it does not hold that varieties that flower in the middle of the blossom season will also fruit in the middle of the picking season. I expect it is similar with blueberries.