Cr8h said:

Any answers?
The Seeds i find in bud or order from seed banks are fully mature and still 1/4x smaller

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Genetics mate .

Yep. The size of seeds directly correlates with whether they're C. sativa subsp. indica or subsp. sativa. Tropical seeds have different environmental challenges than those in drier, more mountainous regions.

Sativa seeds typically seem smaller, in my experience, although all the seeds that I see for sale are usually small. I think this is from the practice of not letting plants grow large and finish fully has also resulted in smaller seeds. A few decades ago, Indica seeds typically had tiger striping, while Sativa, like Colombian or Mexican, were slightly smaller and usually soild brow.
With genetics as scrambled as they are today, I would bet more on the short cycle method of growing being the biggest reason. Decades ago, it often took 5-6 months to complete a grow, which has shortened a lot over the years.