Case clients can't be of different contact type

When CiviCase is set to allow multiple clients I would assume that when editing a case I can add another client of any contact type. I assume so because when you create a new case in the UI you can have multiple clients of mixed contact types.

I have tested and found that once a Case has been created with an initial client, you can only add other clients of that same contact type (Individual or Organisation). Some examples:

• Create a Case with an Individual contact as client. Manage the case and click add client, the autocomplete only allows for Individual contacts.

• Create a Case with an Organisation contact as client. Manage the case and click add client, the autocomplete only allows for Organisation contacts.

• Create a Case with an Individual (first) and Organisation client. Manage the case and click add client, the autocomplete only allows for Individual contacts.

• Create a Case with an Organisation (first) and Individual client. Manage the case and click add client, the autocomplete only allows for Organisation contacts.

I believe this is a bug since you can create a case of multiple client contact types in the UI, also the last two points seem to suggest something is only working off the first client it finds.

Could anyone confirm this is not expected behaviour?