I've noticed this too. Once it actually worried me; I planted a Napa Chardonnay tomato and even when small it began having the telltale purple tints of antho types - which it isn't, it's a white cherry. But I read later it had antho genes in its lineage - aha!
Which vendor? I ordered seed too, although it won't be grown until next year at the earliest.
A pepper seed company called The Pepper Merchant, new this year. I have I think 6 potted plants - all duds looking nothing like they should. Funny, when I started them they were really different as seedlings than any of the others. They hyper grew, and it struck me as odd. Too vigorous. I've only seen that once before, in a hybrid cucumber called Salt & Pepper. I think the writing was on the wall then, I just failed to read it. I'm surprised though a vendor selling only peppers is selling crossed seed? The only reason I even placed an order was to get TM!
It may be that this new merchant grows peppers for seed without isolation. Although it may appear to run contrary to normal selection (for the strongest plants) above-normal growth rate in peppers & tomatoes is one of the factors I select against. In my experience, crosses are more likely to exhibit such growth.
If you're asking about the asparagus peas, I can't help you, I haven't tried to grow those in DECADES (as I don't like the taste of asparagus, why would I?"
Yeah, that can be a problem with some of the seed companies. I have already mentioned how out of date a lot of the Richter's Seed Zoo stuff is. And a lot of the eBay and Etsy sellers are sort of fly by night; appearing and disappearing at a moment's notice, so hard to count on for repeat buying.
I checked out the company's instagram and the good news is they are very open about how they grow and do things. The bad news is, yup, I can see why they might have been crossed! They grow 1000's out in an open field, all together, no row covers. They posted that they had over 1000 trays of seedlings, and they were all flowering even then, likely mixed together. What I find odd is that all the other peppers I got from them grew 100% to type. I grow my peppers in the greenhouse but I don't always keep the door closed when it's really hot, and I'll occasionally grow some outside, no bags. And still, my purity rate is about 98%. In a batch of 50 pepper plants, like this year, I got one cross. So, that all the Thunder Mountain's were crossed seems unusual. And they sent 10 or so seeds in a bag.
