I just went out into my yard and crunched up the leaves of 6 Lemon Zest seedlings and they all had a strong Lemon Zest sap smell like the actual parent. The smell of the sap is strong enough that I had to wash my hands after crushing each leaf in order to avoid cross contamination. I did notice that two of my seedlings growing from the same seed had a slightly weaker Lemon Zest leaf sap smell and these two seedlings are the smallest runts and their leaves were smaller and not as juicy as the healthier seedlings.
I also checked several of my Sweet Tart seedlings and the four seedlings I checked all had that Sweet Tart sap smell. Some seedlings did die after the seeds were planted and I wonder if those happen to be the zygotic seedlings.
Wether it's just dumb luck or some other factors I have yet to consider, the important thing is that this technique of planting polyembryonic seedlings and checking the smell of the sap seems like a totally logical way to get larger trees without the risk of early flowering by completely eliminating the need to graft.
There are still lots of issues that may pop up along the way but many of the issues I can think of are highly unlikely. One issue that could happen is that our cold weather can still induce early blooms even on young, ungrafted seedling plants. The only way to find out if this will happen is to grow out our seedlings and keep track of what happens.
Another issue that may occur is that even though the seedlings have the characteristic sap smell of the actual parent, the fruit from the seedlings may not taste anything like that of the parent. This may be caused by mutations, genetic drift or simply because even though the sap smelled the same as the parent, the seedling was actually zygotic and the half of the genes that the seedling received from its maternal parent was enough to pass on the smell in the sap of the zygotic seedling.
I personally feel that these scenarios are highly unlikely.
Simon