A script as simple as this will  demonstrate the inconsistency:

image create photo .imgobj -file
ttk::button .b1 -image .imgobj  -style "Toolbutton"
ttk::button .b2 -text "Hello" -style "Toolbutton"
button .b3 -text "Quit"
button .b4 -image .imgobj -text " Cancel " -compound "top"
grid .b1 -row 0 -column 0
grid .b2 -row 0 -column 1
grid .b3 -row 0 -column 2
grid .b4 -row 0 -column 3

If I create the buttons with Frameworks created for example with this source <a I get what I call the 'modern' look with style Toolbutton (new screenshot 'modern', below) . If I create the buttons with the latest source, I get the "older" look.

In both cases, I compile Tk simply with 'make -C tk8.6.9/macosx' on the same machine with Mojave.