Dennis wrote: Excess pressure will blow hoses long before a freeze out plug.

Don't count on it.  After a good mechanic (but not a VW specialist) went
through the cooling system on a 1.9L in my '85, I blew plastic 'H'
fitting when I overheated.  After replacing that and while driving while
badly overheated the engine was suddenly gushing coolant.  When the
engine was pulled it had blown out a freeze plug, but none of the hoses
were split.  The plug was laying next to the engine.  The block also had
a crack by the blown freeze plug.  BTW, the over heating problem was
finally found:  clogged radiator.  Cooling had been marginal for a long
time.  The first mechanic back flushed the radiator, all appeared fine.
But the back flush had rearranged the crud to the point that cooling was
near zero.