Pantheon-Web uses Karma for coverage, with the Cobertura reporting format, and it does include branch/conditional coverage data, so it is possible. Also, Jest's own HTML coverage reports do include branch coverage. It must be just a reporting problem. This bug suggests that the Cobertura support may be a bit lacking: https://github.com/gotwarlost/istanbul/issues/729
We need to investigate, and come up with a coverage solution which includes branch information.
Some options which might be investigated:
tweak reporting format options in Jest/Istanbul
create bug fix for Cobertura reporting format in Jest/Istanbul
run tests with Karma instead
generate another format (like lcov) and convert to cobertura format. (Jenkins can only display JaCoCo or Cobertura.) https://github.com/eriwen/lcov-to-cobertura-xml