Hi, K.. You are definitely not doing anything wrong!
My daughter has had breath holding spells, the first one occurred when she was 8 or 9 mos. old, so in my experience it is not just toddlers. In fact, now that she is 3.5, I'm knocking on wood to hope she is finally growing out of them. I did the same as you, researching on the Internet, and what alarmed me was the discussion about not providing undue attention so as to encourage this behavior. Didn't make a lot of sense to me, seeing as the passing out aspect was definitely involuntary, but I guess I bought into the idea of not coddling or being too afraid of upsetting her lest she have a spell. I think this is the concern you are referring to, so I'll try to tell you about our experience and hope it helps you. We did discuss this with her pediatrician who also seemed to prescribe that we shouldn't make too big a deal about it so as not to encourage too much "attention." Of course you want to avoid these episodes as much as possible, but it is an awfully fine line to figure out how to handle.
In my experience, her breath holding spells were always preceded by either a physical or emotional "event" (i.e. falling down, bumping her head on something or someone, or a frustration like taking a toy away or not getting her way about something). These spells seemed to be much more likely to occur when she was fighting a cold or especially overtired, because they didn't occur every time she fell down or had something taken away.
After a while, you could kind of tell when she started crying, and then took in a really giant breath that a spell was likely imminent. The big thing is to make sure you are nearby, so that they don't fall & smash their head when they pass out. When we saw one "coming on," we'd try to pick her up, call her name to distract her & blow in her face to try to startle her into taking a regular breath. Rarely did it avert a spell, but it made us feel like we were doing something. It is definitely scary when it happens, but oddly enough, once you see them turn blue and then come back to normal a few times, coupled with the advice of the pediatrician, I got to be comfortable enough with it happening so that I wasn't so paranoid as to never want her to get upset.
I think the major challenge is how to minimize situations that upset them so much as to result in a breath holding spell without hovering over them and letting them always get their way. That is the fine line I referred to, and I think you have to figure out what works for you.
Sometimes it would happen over the least little thing that I wouldn't expect it (like changing a diaper), and other times something major (like falling down the stairs) would just be a regular old crying 1-yr old. But once I got comfortable that she is prone to these spells, I can't really control them & that she will be fine, even if she passes out, it was a little easier to go ahead and let her scream. I think talking to her pediatrician really helped give me comfort that the spells were not going to be harmful to her, so if they happen it is not the end of the world.
Best wishes - I know how scary it is. I even had to change daycare providers over this issue right around her 1st birthday. Crazy as it sounds, my advice is to redirect when possible, but go ahead and let him scream if he gets upset, just standby in case he holds his breath.
Hope that helps somewhat.