Why are not all of my google contacts syncing to my phone

OK I have a third party online software (Pipedrive.com) that crates NEW contacts in my Google Contacts in a selected Group I have - lets call that group 'clients'.

So Google Contacts creates the contact within the group 'clients' and all of the data associated with it normally.

No problem so far - everything works nice!

The issue is that the contact within group called 'clients' does NOT sync to all my connected IOS devices (i.e. mac contacts, iPhone, iPad) UNLESS I manually go into Google Contacts portal and ADD the additional contact group 'My Contacts'.

I can't find anything on the web that explains this problem.

I would expect that if you are syncing your google contacts with your IOS devices then it should not matter which group they are in!

Hope this makes sense as its a significant productivity issue for us in our business.

Thanks

Clint