The latest version has a different via model implementation after finding excessive time taken importing DEF with vias that had many thousands of cut shapes.
Beware of writing out a techfile after importing LEF/DEF in this sort of case – the via may have a logical line length that is very long – currently the limit on DEF line length (length of statement up until terminating ';' character) is 32768 characters, which is much greater than the spec of 2048, but still easily breakable.