Federal funding for abortions in the U.S. has been prohibited for decades by the Hyde Amendment. Federal funding for abortions overseas has been similarly prohibited for decades by the Helms Amendment.
So readers are literally right when they say that the rider in the House GOP budget resolution that eliminates funding for Planned Parenthood isn't strictly about abortion. Zeroing out Planned Parenthood would be a huge political scalp for Republicans. The practical effect would be to limit women's access to all kinds of health care services, including, indirectly, abortions. But it oversimplifies things to say it's not about abortion at all.
That's not all though.
The Planned Parenthood rider isn't the only abortion-related rider in the resolution. Another GOP rider would prohibit the U.S. from funding any international aid and development organizations that receive money for abortions from other countries. So that rider is specifically about abortions, although in that instance, too, the effects on women would be broader than just less access to abortion services. There's a third rider that targets abortions in the District of Columbia.
The upshot is this: Republicans are targeting abortions with these riders, as well as organizations associated with providing abortion services. It's naive and a bit misleading to pretend otherwise. But there's no question, as many readers have pointed out, that the effect of the riders, if passed, would be far broader and implicate women's health services across the board.