I know you didn't suggest *string* because that would have made your entire argument void, since *string* iswm string2 is exactly the same as string isin string2. My point is that you should not advice people to use iswm just for the sake of it. Especially not for the reason of "not having your scripts setup differently". That's laughable.
Parsing of a webpage will be different for every webpage, and should be evaluated each time differently. Advising to use iswm just for the sake of it makes no sense, so the isin would be perfectly fine. With your example (string*) it would mean string has to be the first part of the string in the sentence. One should only advice this is you know for sure that string will always be the first part. It has nothing to do with the fact that using isin could trip more matches, that may very well be a requirement if the html changes sometimes, making string not always the first part of the line.
isin and iswm are two different operators, it makes no sense to prefer one over the other by default, or to advice others to prefer it by default. The right advice would be: use the right tool for the job, whichever one that may turn out to be.
