Companion bills are tricky in New York, and nomenclature in general is kooky and backwards there, too. For example, NY is the only state I know of that issues new bill_id's for each version of a bill.
But onto companion bills. If you visit the first bill you cited on the Assembly's site (
http://assembly.state.ny.us/leg/?default_fld=&bn=S07790&term=2011&Summary=Y&Actions=Y), you'll see that the actions are weirdly staggered on the page. The last unindented action says the bill was substituted by another bill, which eventually passed. This substitution phenomenon is a dark magic process that even people who work in the NY legislature have a hard time explaining. But in NY, a companion bill is called a "same-as" bill if it's substantively identical to another bill. And because bills can arbitrarily be substituted in place of one another, it's likely a NY bill can have an unlimited number of same-as bills. That's the best explanation I can offer, and since we're talking about NY, I have to end this explanation with a disclaimer that everything I have said might be false and make no sense. There's almost no way to get a straight answer from them on this, unfortunately, but the gist is that you can't assume (at least in NY) that a bill will only have 1 companion bill. I'd be more than happy to connect you with someone more knowledgeable in the Legislature if you're interested in getting better answers to your (extremely valid) inquiry.
And we should definitely be truncating bill summaries, evidently!! Filing a bug on that now...