No worries, I'd never think such a thing!
Remember, the designer and the manufacturer are not necessarily the same person. Manufacture and assembly can go awry in any number of ways, and when I found shreds of twisted metal in the bearings, I assumed something had gone awry (though not necessarily during manufacture).
The logic is that a retainer maintains the balls at an even spacing, and if the retainer is removed, the balls will travel closer to one another, leaving a large gap somewhere. In general that space will be right where you least want it. So when using loose balls you normally use a slightly higher number than you would if they were in a retainer. Anyway, that's the logic.
When in doubt (i.e. after removing twisted metal, dropping an unknown number of balls on the floor, etc), most mechanics will put in as many balls as will fit comfortably in the cup, and then remove one. After I took the shreds of my ball retainer out of the cup, I had room for two extra balls, so I put in one. I haven't ridden the bike yet --there are other issues-- so I don't know if it's all right.
It is a huge pain when servicing something and all the balls fall out. I remember at aged about 11, undoing the steering on my first bike, an ancient Brit, ladies bike with a dent in the man tube, and to my horror, all the balls fell out all over the yard and ran about in the early winter gloom and grit..... It was a right pain, and I only found some of them. Later, I foolishly repeated mechanical bodgery and destruction many more times, next on bottom brackets, later, breaking piston rings on motor bikes, snapping head studs also on motorbikes, warping cylinder heads and eventually, having an inexpertly replaced cam belt snap a week after I had proudly finished fitting it.... Now I just confine myself to riding bikes a bit and pontificating about how they should be maintained.... I learned a bit from these experiments in destroying machines, but mostly, I learned that I should leave them alone and just clean and lubricate them.