I'll try to answer; The conscious works roughly 16/7. The subconscious works 24/7 so let us start by what appears in nature to be the most important, is the subconscious. All life has a natural instinct for survival, but all life has a selective instinct too. It could be changing colour, hibernation or migration etc.
An intelligent species does not need either, but does need purpose, which in the beginning of life it would have needed variety to stimulate that intelligence. This of course would mean that life was evolving as one life. A one energy system producing its own pattern.) This is the only explanation for the design in nature. Yes I did say design; a natural one.
Getting back to the dreams; they seem to be coming from individuals, but if you insert the one energy, then they are coming from one individual system. Lincoln was in touch with the perpetrator, planning the atrocity, which gives the illusion of seeing into the future-a bit like a magician's trick. Helen dreaming as it happened needs no further explanation. Now compare the subconscious experience to a conscious one; We could do something that needing attention, today or three days later depending on necessity. Dr Donald Hoffman proved that all life cannot see accurately, and this is my way, but I guess many see it differently.
Best Regards
Dodin

Your dataset's too small to find a pattern here.

I see no pattern, but am reminded of a dream I had two nights ago. I was visiting a large waterfront structure. A whale had come to a lower part of the building to be milked. I spoke with her and had a very intelligent conversation. She told me something of the migration route of her group. Later I expressed amazement to someone that the whale was so fluent in English. I was told there was some sort of interface that translated her thoughts.

Watch the news for whale communication developments.

It takes more thn two to make a pattern. If you studied statistics, apparent patterns can from randomly by chance with no actual or real significance. This is why science demands that studies be replicated,peer reviewed and verified as valid data and not a random outlier.

documented coincidences?

Yes, that they both saw risks.