TS stated May 10, 2016:
"Our Development and Testing departments are already aware of this issue, as it was first discovered in FileMaker Pro 12."
Thank you for your post.
I have added your comments to the original report. When more information becomes available, I will post again.
4 years to not solve a bug. That is efficiency.
as a work around, you can set Script Trigger for every layout
OnLayoutSizeChange Script "Omit_Toolbar"
Show/Hide Toolbars [ Lock ; Hide ]
Though, user can activate Toolbar, but with the Script Trigger, it will swap back within a second.
Implementing it to hundreds of layouts would be a pain in the ass. Anyway, I'll start coding it in the most critical of them.
I can sympathise. It's a known issue with FM12 which was launched April 2012.