You are correct, seems like the latest kernel is added at the top of the grub list. When installing LTS the result is:
0 LTS Kernel
1 LTS Fallback
2 Current Kernel
3 Current Fallback
Note: Numbering of GRUB menu entries start with 0.
I just edited grub to make Current Kernel the default.
Backup the current grub:
sudo cp /etc/default/grub /etc/default/grub.bak
Then edit grub:
sudo nano /etc/default/grub
Set the default kernel by commenting out the current “GRUB_DEFAULT=” line and changing the “GRUB_DEFAULT=” line to match the kernel you wish to boot:
The 1 above points to the grub Advanced menu, and the 2 points to the position of the kernel in the boot list. In this case the thid entry. It is also necessary to include the above numbers in quotes. Note: GRUB_DEFAULT=2 also works
sudo grub-mkconfig -o /boot/grub/grub.cfg