How to access field data with PHP?

Problem/Motivation

I try to get field data in step 2 of my forms steps workflow within an entity reference view in this step. I'm using the contextual range filter module for this (https://www.drupal.org/project/contextual_range_filter). Within this view I'm using this PHP code to get the date field data from the node in the default edit form mode. This works just fine in the default edit from mode and in any other edit form modes as long as I open them up directly (also with the one I use for the forms steps).

return $entity['node']->field_date->start_date . '--' . $entity['node']->field_date->end_date;

In my forms steps step 2 this is not working. I think because forms steps are different kind of entities!? How do I have to modify this to retrieve the data?