You misstarget why its's a tedious and pointless leading to drawing bad conclusions to level accusations of punishment/punishing of players. With experience the rebalancing for Bob is less and less of a factor over the life of a campaign that is likely to last for a year or more and end in low to mid teen levels. The group is going to be far less reluctant to start adventuring while missing Bob and not as likely to treat it like Tomb Of horrors ten foot pole tapping & such when Bob is a level or two behind. It also means that I don't need to give Bob's PC as much weight as the other players when designing encounters once the gap starts forming and growing, that makes it pointless to rebalance things too much if Bob isn't there for the encounter.Never said XP was punishment, please reread if you got that from what I said. I've also never talked up Milestone as part of this, so trying to tar ti doesn't actually affect anything I'm saying.
And what I said was that your stated intent was to use it as punishment.
And it came across as a rule change how you explained it: "tedious and pointless having to regularly wait for or rebalance the session plans just because Bob knows being late or skipping again won't cost him progress."
There's no indication that that was whole theoretical and never actually happened at your table and might not be an actual problem you'd encounter. Sorry, I read that as a rule change to stop 'Bob' from showing up late or skipping, as you said. If there never was a Bob, you can understand my confusion
Splitting hairs so finely over what exact part of experience or who you are pointing at while declaring punish[ment|ing] after starting out with questionable assumptions like that makes it feel even more like taking offense that someone else doesn't use milestones. The whole argument for milestones against experience too often tends to feel a bit too quick and heavy on charges of gm bullying and shaming over punishment/punishing of players for my tastes, that and the fact that I'm generally considered to be fair as a gm making for even more reason for me to avoid it.