Actually what you would learn in accounting class(es) is:
1. Federal money goes to PP and does not directly fund abortions because there are legal accounting methods to "earmark" the money.
2. Federal money does go PP and helps them fund abortions. This is done by putting the federal dollars in other places, thereby affecting how dollars are allocated to various accounts, including accounts that deal with other procedures. Money from all sources ultimately affect overhead. Overhead includes the costs to fund offices, salaries of executives and other personnel (who lobby in favor of abortion), heat, lighting, advertising (including the sources showing the availability of abortion services), etc. When federal dollars decrease the cost of other procedures, it allows other donated funds to help them cover overhead expenses and others. A dollar earmarked to fund a condom program means that the original dollar that might have been earmarked for that program can now be allocated to cover the abortion expense and/or the portion of the overall overhead burden that abortion comprises.
So the basic argument that federal dollars do not fund abortion is true in the purely legal sense, because there are provisions on how to allocate the funds.
It is ignorant, however to think that federal dollars do not affect the ability for PP to provide abortions. It's easy to see that those dollars do have an affect.
The distinction to me is not important. The government should not be funding abortions, even indirectly, beyond what they do currently with block grants to the states, which provide them through Medicaid on a varying non-convenience basis.