Logical schema is an ER diagram, physical schema is how that is translated to a DB-specific DDL, not to be confused with the physical data storage layer.
Think about all the different ways you can model a list in SQL. E.g. jsonb, array, hstore, 1-M FKs, M-M join table, and all the different levels of normalization.
> I attribute it to too many CS/SE grads who didn't take database-theory electives
Completely agree! But it also makes you realize how the relational model is a poor fit for a lot of data models too - which again many are unaware of. It's not perfect, but its a nice sweet spot for now.
I think we are at the other end of another pendulum swing of databases though. But it's hard to innovate when the prerequisite for success of any new database remains as SQL compatibility.