Because my capable partner here is already on it.
Also, I've said may times before I have 3 to 4 $esp partitions on each of my 3 to 4 disk.
And I had said there is no difference whether any OS should be on different disk or another disk despite many people saying it's best to have on separate disks. Or no difference if $esp should be on the same disk or on different disks.
As to flags, I have (had) all my $esp's flagged.
Then I removed all flags.
Then I put in a flag on a partition where it shouldn't be.
All makes no difference (to me).
And many websites say linux does not require boot flags, only windows boot need it.
But.... some here have problems with booting if the flag is not there.
I myself have helped resolved some issues here where I asked the OP's to put a flag and it resolved the problem.
I suspect that some (not many, BTW, just a few) here needs flags because their disks are not set up properly (partitioned 'gpt' or 'msdos') in the first place and their bios needs help in determining what the disks are. And suspicion alone is never a conclusive determinant.
petsam seriously, I think you are more capable than you think
and I'm more than happy whenever you help out.