https://wildboarfarms.com/product/ameth ... cross-f-3/

In a Wild Boar Farms rarity, a technically “unfinished” variety known as Amethyst Cream XL Cross F-3 is now available publicly. This is an exciting project for anyone who wants to try their hand at breeding their very own stabilized cross or even the grower who wants a bit of mystery in the garden. Although the process is already far enough along that all the differing fruit are tasty and favorable, each seed will yield its own size, color and flavor of Amethyst Cream XL Cross F-3. As an F3, this strain is still early enough into the stabilization process that it still throws wide range of finished fruit; each of which can be made into its own unique variation with selective breeding. The ripened tomatoes are relatively uniform in size from plant to plant, resembling an enlarged cherry tomato. Colors range from yellow, to red, to orange, and can even display splashes of the deep blue from anthocyanin

Many vendors over the years have offered seeds of unstable crosses for you to stabilize as you wish and then name yourself. Marianna's seeds did it as well as do Delectation of Tomatoes, J and L Gardens and Double Helix Farms. The seeds offered in this case seem to be further along than do seeds from the others.

Interesting, I’ve never seen it, but I’m also new to this game.

F3 can be a fun generation to grow. I know I like surprises and mysteries so this is how you become addicted to breeding tomatoes.
But is it cheating? Naw, why worry about that. The point is to enjoy the selection process and the surprises.
The only thing you missed out on is making the cross - something that is really not difficult to do, so you might decide to do your own if you enjoy the F3.
The reality of most breeding projects, is that you do have to weed out the 'not as tasty' 'not as productive' 'just wasn't a healthy plant' 'what-a spitter??' and even sometimes a whole row of fruit that are destination sauce pot, and a cross that's not worth growing any further.
So what's wrong with a little cheating?