The frame resets the tolerance settings and you have to set the values
again for it.

   \defineframed[myframe][align={flushleft,stretch,verytolerant},offset=0pt]


BTW: You can also disable hyphentation with the “nothyphenated” keyword
for \setupalign (and the align key).

\starttext

\startalignment[flushleft,stretch,verytolerant,nothyphenated]
   supercalifragilisticexpialidoc + supercalifragilisticexpialidoc +
   supercalifragilisticexpialidoc + supercalifragilisticexpialidoc
\stopalignment

\startframed[align={flushleft,stretch,verytolerant,nothyphenated}]
   supercalifragilisticexpialidoc + supercalifragilisticexpialidoc +
   supercalifragilisticexpialidoc + supercalifragilisticexpialidoc
\stopframed

\stoptext

Wolfgang