ABEC numbers are not related to the size at all. The industrial size designation is independent of the ABEC ratings or even if a bearing has an ABEC rating. The standard skate and board bearing is 608. The micro bearings are 688.
ABEC ratings have nothing to do with ultimate speed or quality.
ABEC ratings are for the runout or the ability to wobble. This is important for machines running at very high speeds (over 200 mph on a board). To get less runout, the spacing between the parts has to be smaller, which can cause more friction.
ABEC became popular for skates and boards because most of the early ones used a bearing spec called Precision. Precision is anything but that. If you twist them sideways, you can see them turn. ABEC 1 was a huge improvement. The difference between ABEC 1 and ABEC 9 is tiny compared to the difference between Precision and ABEC 1. Marketing people realized that they had a number and people will assume that higher numbers are better than small ones and decided to hype the ABEC ratings.
ABEC numbers are self listed, they are not "graded". If your bearing is designed to ABEC standards, it does NOT cost any more to claim it.
Most skate and board bearing companies just buy standard bearings from a bearing manufacturer. Setting up a factory to make bearings is expensive and they need the volume of the industrial market to make it worth doing. Bones has their bearings made by several makers (some in Switzerland, some in China) I don't know who makes the Twin Cam bearings. Zero Drag was a brand created by Pure Bearings which is a US company.
Some of the higher end companies for skate and board bearings realized that the ABEC specs require such small gaps in the bearings that they were slower and that the spec does not include side to side bearing ability. They have created their own designs that open up the spacing and make them less sensitive to slowing down due to side forces. The larger gaps mean that they cannot even meet the ABEC 1 spec. Sometimes they join the hype and give the bearings a high number but never actually claim the term ABEC.
Note for SSP.
It is not the tolerances (the variation from part to part) but the gaps between the parts that limit the runout of the bearing for the ABEC standards. You can have very SMALL tolerances (small is better) in a really poor bearing.