For evolution you need to actually wait while the organism becomes an adult and see how it behaves. Without it you don't know in which direction your changes move the organism. If you could know it only from genes you could simply edit the genes without having to create embryos from embryos.
Honestly I'm not sure you're even likely to get a viable embryo at the end the GPs procedure.
A large -- up to 1/3 -- fraction of fertilized embryos are not viable, largely because of chromosome abnormalities. Sometimes this happens quickly, before you would really say someone was pregnant, but people don't usually talk about their pregnancies in the first trimester because miscarriages are likely for this reason.
Depending on how well you can sequence the genome and forecast viability of the intervening steps, you'd just be compounding this probability each time.
And as you say, without the intervening "natural selection", there's no real evolution, just an increased mutation rate.
There is one interesting thing you could do, which is probably unethical under many ethical systems, which is that you could use the process to generate "many-parent" babies. Take samples from N people, and in a few days or weeks you could produce an embryo which shares all of their DNA (equally, if you start with a power of two). Sure, it would be functionally (and actually, since you have the intervening embryos) grandchildren or great-grandchildren instead, but I could imagine someone wanting that.
