It's a very astute observation. As the terms "ethical" or "green" are merely marketing terms with no legal meaning, you really do need to read through the bumpf on a particular investment to establish the credentials of your particular investment.
Look out also for "positive selection" and "negative selection". The latter takes a list of stocks and then simply filters out some. (...e.g...."We won't invest in companies that do this, that or the other.") The former actively seeks out companies that meet criteria. (...e.g. "We only invest in companies that do this, that or the other.") Positive selection tends to be "greener".