When it comes to small seeds, the bigger issue is their size relative to the other seeds from the same batch. If you have a bunch of seeds from the same cross, the smallest seeds have a higher chance of not being viable.
You can’t really compare the size of seeds from unrelated crosses, since a lot of natural variation in seed sizes exist.
And don't be fooled by some nob into thinking bagseed are shite either. Sure, you can get some absolute garbage from it. But, there's a good portion of what's "named" stock that came from baggies.
The biggest issue with bagseed is that they’re almost guaranteed to come with herming issues, since bagseed is nearly always pollinated by a plant that hermed unintentionally.
Yeah, lots of elite genetics came from bagseed. But these strains also originated back in the day when prosecution, lack of knowledge about breeding, and lack of access meant that bagseed was often the only way to obtain new stock.
We don’t live in those times anymore. Much of the USA can legally grow marijuana, we have dozens of seed banks IN the country with elite genetics. You could play the lottery and hope your bagseed has the one in a million chance that it’s got something elite. Or you could buy something from any of the dozens of well-respected breeders that bred their elite stock with intention, and have tested their crosses to ensure their quality and stability. For those in more restrictive countries, bagseed may be the only viable option. It’s certainly better than nothing. Thankfully, many of us don’t need to rely on that anymore.