yes that’s normal it’s graphics card being reset by new kernel.
btw current version of purboot seems break intel graphics so if you chose compositing desktop environment like kde, expect some glitches, random crashes, reboots, or screen blinking.
some of those look like hardware failure, while it is fault of firmware.
solution: temporary switch to coreboot+seabios
supplemental explaination:
pureboot is nothing more than small embedded linux, that does verification of HOTP and TPM.
then calls kexec to load new kernel (your chosen linux) then with kexec() try to boot new kernel.
at this point hardware control being handed over between old kernel (pureboot) and new kernel (distro you chose). at this point things being to complicated to explain, but yes temporary graphics glitches are expected.
the fact that something is wrong with intel graphics after actual OS being booted is being investigated.(random glitches i mentioned above)