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.
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.