By suggestion of @dimstar, to “point at any documentation that confirms that pic and shared makes no sense together”, I am citing the documentation, https://www.gnu.org/software/libtool/manual/html_node/LT_005fINIT.html thus:

by default, libtool uses PIC objects for shared libraries and non-PIC objects for static libraries

Static libs are not built, and shared is already PIC, so --with-pic has no effect.