[jtbayly]

You don’t appear to be able to say anything helpful about what “model” means in this discussion. The only explicit claim you made (that they were different because they would have been implanted in a womb for a week already) was incorrect. Some would likely have been implanted for a day.

[Retric]

Your timeline is off, the egg can take nearly 2 weeks to implant but that requires a delay in fertilization. This 14 day timeline is specifically in reference to fertilization not the release of the egg.

The discrepancy exists because people can track the day of ovulation and hormonal changes from implantation but actual fertilization has no obvious signs, unless your doing IVF or something and looking at the actual egg.

That said, extreme outliers may exist but that’s not what we’re talking about.

[jtbayly]

IVF is exactly how one would implant these embryo "models," and that's why I brought it up in my first comment.

Here's an example of how IVF embryos are graded at day 6, prior to implantation:

https://flo.health/getting-pregnant/trouble-conceiving/ferti...

I think you missed the fact that these models start at the equivalent of day 7, so we're right in the same time window of implantation. Unless you are claiming that exactly at 6 days after fertilization is when every single embryo implants, and at 7 days it is simply too late. But your whole point seems to be that the window is hard to observe, so I doubt that's what you mean.

At any rate, I still see nothing to indicate that these "models" are not simply embryos. I think they are intentionally calling them models so that they can skirt the legal requirements about embryo research.

Unless of course you can point me to something that is actually different about one of these models vs an embryo. The whole article is about how they are the same.