While that'd be a lot less risky than no pressure cooking at all, it's not fully safe. For complete safety, it's important that the actual canning processing be pressure cooking.
The problem is, even if the jar is sterilized, and the food is safe before you put it in, there's no way to completely ensure that no additional spores make their way into the jar before you close it. I don't think there's really any good way to assess the actual level of risk, but it's a "why take the chance" thing - in the unlikely event the food does get contaminated, there'll be no sign, and the botulinum has been given an ideal environment to grow in.
Note also that in order to actually sterilize the jars, killing any botulinum spores, you'd have to pressure cook them too, so you already need a canning pot big enough to hold them even for this plan. (It sounds like maybe you were thinking of using just a boiling water bath, but then they're only safe for use for high-acid foods that you can in a boiling water bath, not for low-acid foods that you need pressure canning for.)