>>100-103
Read it again. That section does not imply that
modified GPL code is considered GPL code; that section does not imply that
modified GPL code is considered publically available; that does not imply that both these things are happening to modified GPL code.
Here is a hypothetical to where this quoted section applies:
1. Person X obtains the GPL3 software, Foobar.
2. Person X modifies Foobar and calls the result Bazqux
3. Person X conveys a copy of Bazqux (and associated code) to person Y
This section implies : person Y will receive the whole of Bazqux under GPL3. The section does not imply: make a modification to Foobar and therefore, your modifications are considered under the GPL. This section implies: person Y obtained a copy of Bazqux because YOU conveyed a copy to person Y. This section does not imply: make a modification to Foobar and therefore, you modifications are considered publically available.