Definitely there is no mirroring of all information. There is probably no mirroring at all.
I did not really looked into the pagefile in last couple of year. Last time I was concern with that was windows 7 and since then I assume not much have changed.
In typical home user scenario both cases when pagefile is used (read and write) are kind of critical events in which first the system wants to get rid ASAP of least used memory pages, because some other program or subsystem want to allocate more memory. Then second, when page-not found happens and then that page is needed ASAP.
Basically you do not want to waste time when you need to write to pagefile and you would write faster if only you write one page to one drive.
In general even SSDs (though much better than HDD) are very bad memory compared for RAM. In general you should avoid needing it.
I would assume that putting pagefile on multiple SSDs is rather a way of distributing SSD wear than doubling it.