What does that mean and why is it a thing?

it means Larian didn't test their game and without it act 3 will crash at load time

they have since lowered the graphics [patch 5] to make it more old system runable but really a SSD should still be used if you want to finish a run

also note the current state of the game is pretty busted

They did test it on HDDs and even have an option for it in the settings.

I played on an HDD for a bit. It wouldn't surprise me if there are some disconnects in multiplayer but the big thing was load times. If you can tolerate long load times then it's playable on an HDD.

It's also 2023 and tech moves at lightning speed.

I bought a 500gb SSD for like 40 bucks. Don't act like you need high end groundbreaking tech to run this game.

This mean, we have year 2023, not 2003.

Most games have needed an SSD to stream textures and assets at any acceptable rate for years at this point. Grab a cheap bigger SSD they are relatively inexpensive these days. If you are still running on spinning rust getting an SSD (even a SATA one though NVMe preferred) will probably be the biggest upgrade you could possibly do for yourself unless youe GPU is super weak. And unless you are doing some type of extremely heavy content production you will never even get close to the TBW of modern SSD's for many.. many years. Normal users.. even "heavy" users don't need to worry about that.

The game runs very well for me with an SSD, and the difference between HDD and SSD in games can be dramatic to say the least. Installations and file load times are much, much faster, especially for modern games. There are games that already only supporting SSDs... and it will only get worse over the next few years. As for the game being busted, "no it is not". If you only want to use HD drive than do so, it does support it (check box in options).