I always find arguments about definitions to be so much fun!
The only photograph that I can think of as being essentially "honest" or "true" or even "straight" is a copy photo of a two dimensional object - such as a document.
Otherwise, every photograph is an allegory - it hints at what might have been in front of a camera, rather than being an exact representation of it. Sometimes the "hint" is really clear. Other times it is really murky.
Among other things, that is why, absent legislative intervention (e.g. traffic cameras), photographs alone can't usually be used as evidence in court. They require corroboration from other evidence.
The OP really likes books of photography. And if you spend a lot of time with those, or at galleries, or reading photographic Art websites, you will get a sense of what sort of photographic trends are current and popular and attracting higher prices in the Art world, and showing up on gallery walls - both real and virtual.
Photographs of things found in the world, presented simply without much technical manipulation, don't seem to be trending. Any trend toward that type of photography is certainly quite quiet. But being less popular doesn't mean death.
FWIW, I wouldn't use "straight" as a definition here. If I was going to look for a description, I would probably do so using negatives - photographs that don't have certain things in them. This is the sort of definition that Sirius seems comfortable with.