It is very rare that anyone sells, let alone buys (intentionally) indian blue worms.
The big nation-wide composting worm vendors - yes probably the one(s) you're thinking of - often sell blue worms labelled as red wigglers. Look for a "composting worm mix" label, or a species disclaimer on the website.
In my opinion, it wouldn't be that big of a deal, but they are also advertising on the same page how red wigglers are the best/perfect composting worm, then selling you blue worms instead. If you truly believe indian blues are comparable composting worms, why are you hiding the fact that you have a mix of blues?
If you couldn't tell, I have also been a victim of being told I was buying red wigglers, but was actually sold indian blue worms. I think sometimes these companies rely on the customers not knowing the difference.
My suspicion is that a big worm vendor received an influx of worms from India (worm composting is huge there), which contained Perionyx Excavatus, which then populated their bins, and the bins of whoever sourced any worms from them as well, which includes other worm vendors.
Why I do not prefer PEs:
They will overtake your worm bin and can quickly overpopulate/overtake other species. They will reproduce closer to their maximum rate when other species won't be at maximum reproduction.
They are very finicky, will leave the bin when the slightest upsets happen, which includes changes in barometric pressure.
They are tropical worms (like ANCs) and will not survive lower temperatures.
Despite anecdotal evidence, scientific journals find that they consistently eat slower (though only slightly) than red wigglers. See the source above.
Not as serious - The way they move gives me the creeps. They don't move like other earthworms.
Why you should pick Indian Blue Worms
They are prolific breeders even in less than ideal conditions. If you are looking for a worm to use as food for another pet, blues could be a great pick.
If you do not mind mixed species there is some benefit in that however the conditions are in your bin the worm species that handles it best will reproduce and populate your bin. There are other minor advantages to each species that you can get by using a mix.
If you want to keep a good population of red wigglers or european nightcrawlers I would avoid adding blues to your worm bin as they will outpopulate other species.
There is no best worm, it totally depends on your circumstances and your goals. For beginners, I always recommend the red wiggler. They are going to be the easiest worm for an inexperienced worm farmer.