Generally these stricter defaults involve calling sign or csign inside a
simplifying function. This leads to undocumented behavior:
(%i71) m : matrix([abs(x), log(exp(sqrt(x)))],[5,7]);
(%o71) matrix([abs(x),sqrt(x)],[5,7])
(%i74) m : matrix([log(exp(sqrt(x))),abs(x)],[7,5]);
(%o74) matrix([sqrt(x),x],[7,5])
The order matrix elements are simplified isn't documented. Another example
(%i85) m : matrix([abs(x), if x > 0 then log(exp(sqrt(x))) else 42],[5,7]);
(%o85) matrix([abs(x),if x>0 then sqrt(x) else 42],[5,7])
(%i86) m : matrix([if x > 0 then log(exp(sqrt(x))) else 42, abs(x)],[7,5]);
(%o86) matrix([if x>0 then sqrt(x) else 42,x],[7,5])
Finally, sign & csign are somewhat slow functions (speed depends on fact database).
--Barton