Good historical fiction is accurate. Like you said, it should be true to its time period – IF that is its goal, if it is out-and-out historical fiction, as opposed to something with an element of fantasy or satire which stretches the truth or changes elements on purpose.

Examples:

The Eyre Affair etc by Jasper Fforde, set in the 80s, I consider to be fun, funny, and fantasy, not historical fiction.

Libba Bray’s trilogy is, IMHO, historical fiction MIXED with fantasy – I think she gets the Victorian time period right, and infuses it with magic and supernatural abilities, all the more reasons why I LOVE IT.

Flat-out historical fiction would be novels like Hattie Big Sky. Have you read it yet? Oh, SO good.

I often explain the difference between historical fiction and classics that were written during/close to the time period in which they are set that now APPEAR to be historical fiction to people.