The TCP/IP model includes L2 vs L3 vs L4 (i.e. it's not limited to modeling just the TCP/IP portion it is named after), it doesn't include the rest of the cruft the OSI model does nor any expectations on how those layers were supposed to tie together (which never happened the way OSI laid things out anyways).
If you ever spend any time with more than your standard wifi + NAT connection understanding L2 vs L3 vs L4 becomes very handy.