The issue occurs when installing the Enterprise Portal on a claims web application, so actually you will also face the same the issue on SharePoint 2010 when using claims. The issue only impacts Safari browser; in IE or Firefox you will not see the issue.
There are two solutions to this issue
- to install Enterprise Portal using “Classic” mode authentication. To do it you need to run PowerShell script to create SharePoint Application: https://technet.microsoft.com/en-us/library/gg276326.aspx and then install Enterprise Portal on such web application. On such an Enterprise Portal you will not be able to enable Forms or ADFS authentication and also Office Web Apps will not work, but I guess that should not be a problem
- if you plan to use Forms https://technet.microsoft.com/en-us/library/hh575253.aspx or ADFS https://technet.microsoft.com/en-us/library/dn621030.aspx authentication you can go ahead and also set it up as in the documentation. Our tests show that as long we have one authentication provider configure the issue is not appearing neither for claims user nor for windows users.