my understanding of the term
They show no development.
It is not enough to posit a means or mechanism by which the universe might be generated. One must also make plausible the model by showing how it might be developed into a complete universe exactly equal to the one we inhabit. In no case would I expect a completed xerox copy of the rules of this universe. It is too complex at any other than the most fundamental levels of observation. Hence, I have said, "The proof is in the details ... but not the minor details". If one could indeed get all the major details right, one could expect all the minor ones to follow in due course.
But, because all such models must necessarily be generated by a single person, all will be simple prototypes and little else.
All the so called ex nihilo models I have ever found offer no development whatsoever. There is just a hypothesized beginning then ... nothing. Where is gravity, the electro-magnetic force, etc.? ... why does matter behave in exactly the manner it does? ... and what of the pure numbers associated with the experimentally observed forces? All these must be generated as a direct consequence of the initial postulates which is why the "standard model" is not a genuine ex niholo model of existence.
Models derived not as direct consequences ...
The standard model merely states that there are an infinite number of possible universes in existence and this is but one of them. Therefore, their conception of ex nihilo is "It is here because there is nothing to prevent it from occurring", i.e. it isn't forbidden.
Hence, their "derivation" is indirect. Anything is possible provided that it is logically consistent. Which brings us to the last condition ...
It must make disprovable predictions
Even the standard model makes no origin based predictions at all about the state of the universe. It is entirely empirical with an ad hoc beginning put on (from nothing - by virtue of not being forbidden). Predictions in the standard model start from the empirical base ... not ... from a postulated beginning by logical necessity.
My model does make such predictions ... dozens at present ... and ... many presently falsify my model. Occasionally, I find a way to simplify the model to take care of an inconsistency ... but I never make it more complex to accommodate "things that don't fit". These are the clues that something is wrong with my thinking ... or ... that the entire prototype is false from its fundamental assumptions (postulates). I stick with it because I have the utmost confidence in those simple postulates and see no way to any ex nihilo derivation except through them.
If I'm wrong in those ... then ... it must be that the standard model's base is correct ... we are here because it is simply not forbidden.
There are also objections appealing to semantics or arbitrary definitions.
I have had people tell me that my ex nihilo model is wrong because you obviously can't get something out of nothing ... which is simply a denial of the historic discussion (at least centuries old if not more). So they assert that I am disproven by definitions rather than by the only criteria fit to this end ... the inability to provide development from an initial state (the fundamental postulates) to what we actually observe ... in terms of ... logic, mathematics and geometry.
And the arguments I have seen which debate the meaning of this or that word are without end. They are repeated in various guises ad nauseum. I am ever amazed at how many ways different people can see the same thing. It is no wonder that "eye witness" testimony is shaky ground in court.
Hence, I have no illusions about convincing anyone at all that my model is the correct one. It is sufficient that they simply understand what I am talking about so that they might be in a state of
Plane of Mutual Ignorance