I have not tried the Windows version yet but best guess.
The same occurred when going from Gimp 2.6 to 2.8 The 2.6 installation was removed but the 2.6 profile remained.
The reverse was not true. With 2.8 installed you can (re)install 2.6 without affecting 2.8
edit: hmmm..that is not going to work. Gimp 2.10 shares the same folder name as Gimp 2.8 - C:\Program Files\GIMP 2
Bear in mind that Gimp 2.10 is 64 bit, any old 32 bit compiled plugins will not work. There will be a way but a portable Gimp 2.8 might be easiest.
The same occurred when going from Gimp 2.6 to 2.8 The 2.6 installation was removed but the 2.6 profile remained.
The reverse was not true. With 2.8 installed you can (re)install 2.6 without affecting 2.8
edit: hmmm..that is not going to work. Gimp 2.10 shares the same folder name as Gimp 2.8 - C:\Program Files\GIMP 2
Bear in mind that Gimp 2.10 is 64 bit, any old 32 bit compiled plugins will not work. There will be a way but a portable Gimp 2.8 might be easiest.