That's not really patching though, any more than any use of function pointers is patching.
replyThere's a part of the .so ELF file (the Global Offset Table aka GOT) that has to be modified with all the addresses of the functions being imported, which of course vary from process to process.
replyIf not patching, what exactly would you call modifying part of the file?
And the got is just a big table of pointers like any other table of pointers your application manipulates as it runs.
replyThis isn't meant as a reductive take, but instead that there is a difference between completely describable in C like the contents of the .got section, and something like a .reloc section that actually has to understand the generated assembly in order to build the relocation table to load and link the executable. Both are linking, but I've saved "patching" for more brain surgery esque techniques. Like on mips, the jump instruction immediate is the bottom 26 bits of the absolute address of the target, so you're going through and modifying all of the jump instructions if you load it to somewhere it wasn't linked at.