In the Views filed configuration panel, there is a section titled "Multiple Field Settings" (only for fields that support multiple values).
Under that section, there is a checkbox with the label "Display all values in the same row".

EFQ does not seem to support that option, precisely, the checkbox cannot be unchecked. Is there a particular reason for that ? Is there a work around ?

Context : Vanilla Drupal Install. Latest Views, Mongo Field Storage, EFQ version 7.x-1.0-alpha3+14-dev

many thanks