Not sure if this is by design but it would be nice if all toolbars behaved in the same way. Version information below.
JohanOS: OSX
Machine: MBP 15"
Version: 3.21.2.0 (3.21.2)
Internet: QCAD.org
Build Date: Jul 9 2018
Revision: f9cea14
Qt Version: 5.10.0
Architecture: x86_64
Compiler: Clang 8.0.0