Depending on where you live. The state of Minnesota has a law directly written by labor activists called Earned Sick and Safe Time, which gives 6 days of sick time to every employee in the state. Mental health is a valid reason to use it.
If you're only taking mental health days when you're burnt out, then you're not going to actually help yourself with a single mental health day. There are other signs you need to look for that only you know about. My other signs include a nonspecific dread/anxiety about work without reason, extreme exhaustion, or extreme anger before my shift. Mental health is an "all the time" thing, and shouldn't be gate kept like what you're doing.
I default to the "I am having vision problems" and leave out the "I just can't see myself going in to work". Or the "my vision in life isn't lining up with works vision".
When did "call in" change to "call out"? And why? You "call in" to work to tell them you will be out.
It feels like it was in the last 5 years or so, but all the new people (younger than me) at work now say "call out," and I don't understand the lexicon shift.
In my experience "call out" was more common for a shift-style job at a place with many low-level, younger employees. Think fast-food, retail, etc. Maybe had to do with the perception that another employee is just "slotted in" to replace the shift? Regardless, these same people are now getting older and the term has spread to other types of jobs...