This test case on concurrent_drops_and_create.js fails on v7.0/v6.0 multiversion suites that use v6.0 binaries. The reason is that on v6.0 binaries findAndModify in a multi-document transaction does not preserve snapshot isolation when reading at a timestamp earlier than a collection drop – this is a documented limitation (SERVER-84760), that has been fixed on v7.0+.