I was just using the fire and plague as an example, not as a definitive reason for the Act. As you'll note from the preamble to the Act its concern was primarily the estates of people dead at sea and not recovered;
An Act for Redresse of Inconveniencies by want of Proofe of the Deceases of Persons beyond the Seas or absenting themselves, upon whose Lives Estates doe depend.
X1 Recital that Cestui que vies have gone beyond Sea, and that Reversioners cannot find out whether they are alive or dead.
I have probably got as much knowledge in law, especially English law pre-1900, as the subject of this thread does. Nevertheless, there is one other thing that I would point out, and it's in the first line of the Act itself:
Whereas diverse Lords of Mannours and others have granted Estates by Lease for one or more life or lives, or else for yeares determinable upon one or more life or lives And it hath often happened that such person or persons for whose life or lives such Estates have beene granted have gone beyond the Seas ...
This, I think, is a reference to a life estate
, or life tenancy, which is a type of land ownership that lasts only for the duration of someone's life. Once that 'measuring life' ends, so does the ownership, which 'reverts' to someone else (the 'reversioner'): often the original owner, but sometimes not. Maybe you can see how this would be really attractive in a feudal-ish system, where the lord of the land wants to get people settled on it but doesn't want to give up control of the land permanently. The measuring life doesn't have to be the owner's—the owner could sell on the life estate to a third party, or I think it could even be set up as a tenancy based on some third party's life—but on the other hand, once established, the measuring life stayed the same: if I held a tenancy for my life on my house, and gave it to my son, when I die, my son would be dispossessed.
You can see how grossly inconvenient this could be if, rather than dying in a public duel, or something, I were then to go across the sea and vanish. Now the reversioner wants the land back, and thinks he's entitled to have it, whereas my son wants to keep his home. Up to a point, the reversioner would have to prove my death in order to trigger the reversion; the CQV act simply established that point at seven years out, beyond which it'd instead be up to my son to prove I were alive. (The second part just deals with cleaning up the circumstance where I return 10 years later, having not gone overseas at all but just had a really long night in the pub.)
Who cares, besides careless seafarers and pub customers, and beleaguered law students who still have to study the accursed things? Well, it seems to me that it takes it even further away from the strawman proponents' concept of things. This law just has to do with tidying up a semi-common way of holding land at the time. I could see a grain of truth in the strawman interpretation if this had to do with estates: for example, if, after the living man is unheard of for seven years, via the CQV Act he is presumed dead and the Crown takes possession of his property on behalf of his estate. (Assuming he dies intestate, I guess, in which case it seems like writing a will would be a much more efficient way to address it than running around writing a lot of gibberish letters with stamps and red thumbprints all over them.) But it doesn't have any connection even to that.
Maybe, and only maybe, there is some underlying idea that a birth certificate constitutes a life tenancy in a human body, and once the body's life expires, so does the tenancy. There's a certain stoned philosophical logic in that, and woolly though it is, that at least has a tenuous connection to the CQV Act. (That is, if the Crown grants the life tenancy via the birth certificate, presumably it is the remainderman as well, which leads on to all of the other stuff. Not that it's not actually nonsense.) You never seem to see it explained just like that, though. I guess either that someone needed to rewrite the script to add a role for the Zionist Bankers, or that someone needed to make it complicated enough to hide the hazy theory underlying it, or a bit of both.