NN

To Cheryl (comment # 17);
It is easier to form elliptical statements in Greek but even English can give the type of statement which you “don’t think possible.”

“John and Katie are going to support each other, and Max is going to do the same for Steve.” – We’ve gone from a reciprocal to a non-reciprocal statement.
It’s more awkward in English but possible nonetheless.

Before you say it – of course this doesn’t prove that the second is not non-reciprocal; it is just compatible with it. So you have to look to other information to find out whether or not the second construction is also reciprocal (which is why looking at other parallel instructions in the epistles is necessary to be certain of correct interpretation).