And no, I don't think I'd particularly care for your guess about why the FLE posits this as an initial premise, precisely because you'd guess that it's because of theology. That's simply not true. It's based on the notion that if humans were to seed a planet and front-load, we would almost certainly choose to front-load Metazoa and try to front-load intelligent life forms, would we not?
No, because apparently that means we'd have to wait an awful long time before we got any return on our investment, assuming that we wanted something other than a bunch of prokaryotes glooping around (and presumably that is what your Designers wanted or they wouldn't have front-loaded them to evolve into things other than prokaryotes). If you
know in advance the genomes of the organisms you want to exist, then you might as well just make those organisms.
So far as I can see, the only conceivable point in seeding a planet just with undistinguished blobs is as an
experiment in
Darwinian evolution, in which case you wouldn't front-load anything. This still presumes a willingness to wait a few billion years to see the results of this experiment, but at least there'd be some point in waiting. If you know what you want to happen, on the other hand, why not just make it happen?