It's not surprising to hear such advice from PostgreSQL consultancy shop: don't bother and relax until the day you desperately need PostgreSQL consultancy! /s
Seriously though, the main point stands. PostgreSQL isn't designed with "distributed" in mind, so try vertical scaling tricks first.
The skepticism is founded, but there's some truth.
PostgreSQL (and traditional RDBMSes) aren't built with horizontal scaling in mind. That's both a blessing and a curse. The curse is obvious. The blessing is that it means that they will let you get much further with vertical scaling. Especially if you take the time to learn how to tune them.
Support for horizontal scaling comes at a cost. When I've done performance analyses, I regularly find that parallel and distributed implementations spend most their wall clock time on synchronization and communication. Occasionally more than 90%. That creates a big up-front cost you need to overcome before you see a net benefit. It also leads to a sort of horizontal scaling version of the rocket equation where returns can diminish rapidly.
Seriously though, the main point stands. PostgreSQL isn't designed with "distributed" in mind, so try vertical scaling tricks first.