Actors who post birth-day but not year?

Okay, I'm both a filmmaker as well as a film scholar/former-critic, and have even acted a couple times (generally as a bit part or extra), so I both can and can't understand this common practice now where actors post their birthday on imdb etc but not the year (like what's the point; so I can wish them a happy birthday but not know how old they are?). There's a lot who straight-up lie about it and it's often pretty obvious, but I'll still take it over the awkwardness of just posting a day.

The film business is very shallow and it's all about casting people who fit their roles. Age does play a part in many, many roles so people casting like to know the accurate age-range of the actors they are casting. There's nothing more frustrating than putting on a complicated casting session and a bunch of actors show up who look completely different from their headshot. Yeah I'm old-school and prefer in-person auditions over when actors send in a video of themselves. There is an issue too of casting a bunch of high school students and you have 30-year-old actors vying for roles that should really go to teens, and it looks bizarre when you have a scene with teens and 30-somethings all pretending to be in class together.

Also from a casting / film scholarly perspective, it seems downright cowardly on the part of the actors. Established stars (almost) always have had their birthdays listed for ages and it doesn't seem to limit their roles. I've seen a few remove their birthdays from IMDB but you can still find out pretty easily with a little digging (or even merely jumping over the TMBD). For up-and-comer actors, I get that they're afraid that having their age listed will cost them roles, but I think the jury is still out on whether that is true or not. As someone curious to know an actor's age, it kinda forces you to have to look at their earliest credit and guess if they were an adult or a child actor at that point, then mathematically add to it in order to determine their current age. I know discrimination with certain groups (such as age) in hiring isn't legal, but I think casting is a de facto exception for a litany of reasons. Say, like you're generally not going to hire Denzel Washington to play a Roman Emperor.... oh wait. Well you're never going to cast Patrick Stewart to play a 10-year-old Egyptian child in a serious drama.

Personally I think if I were to seriously pursue acting or give advice to actors, I would say to be as transparent as possible about things like your age and birthplace. Sure it may cost you some roles but it also makes it look like you have nothing to hide, which may do the opposite. You can say your age is "nobody's business" but I disagree as it can (and will) always be guessed at; you're just making other people have to work harder to guess at it which they may not be too inclined to do.

Thoughts?