I have so many thoughts on this...
Firstly, that people should really use the word 'acquintance' more often. 'Friend' should be reserved for people you love and have a deep meaningful relationship with.
Secondly, how would they tell you? 'So by the way, Jackie, we are totally loaded'? Discussing your finances with someone who isn't directly impacted by your finances is weird full stop, but announcing your finances to someone who is less well off would just be a very bizzarre conversation. How would it even start?
So I happen to be quite wealthy if that helps for context. I'm around 'normal' payday to payday people a lot of the time, apart from maybe grooming/body language, I don't give out any overt signs of wealth. Fair, I don't drive an old banger, but it's not eaxactly an Aston Martin. I may be dressed head to toe in expensive items, but they aren't visually branded, so unless you know fashion well, you wouldn't be able to tell. I don't join conversations about money/cost of living, or just nod along.
Most people I know probably assume I am saving for my first house and don't have much of a pension. For example, when I buy or sell a property or similar, I wouldn't mention in.
Whereas a lady at work is currently doing it and we all know every tiny detail, her deposit, rate and whatnot. Generally all my colleagues seem to have disclosed their mortgage rates to everybody!
I don't want to make people feel bad or create gossip and barrier, so avoid money conversations all together - from your reaction I can see why your friend may have done that. For example, people that are more comfortable than others routinely get slagged off or be expected to pay for everybody, and nobody wants their money to become 'a thing'.
I sometimes talk to someone who thinks she's very well off. She'll brag about her holiday home or an event they went to because 'they weren't really interested but it was fancy so they paid x'. I say nothing and just nod and smile as my goal is not to create a comparison moment for them and rain on their parade.
Now, I have always had a lot of contact with other people who are wealthy or very wealthy, including billionaires. When one is in the company of their financial peers, one may talk about money. Because you're in the same spending bracket and with similar concerns or money decisions.
If two people are deciding between the latest Ferrari or Lamborghini, it makes sense for them to chat freely and openly about the merits of each car. If they are having coffee with the Ford Fiesta guy, save for specific circumstances, it's extremely rude to mention about buying a 100K car if it's not a shared topic with the other person and all it'll achieve is make them resent you or think you're a show-off. So you don't, and talk instead about your shared interest in coffee.
Similarly, a billionaire wouldn't talk about their manor renovation and where to procure the best materials with me.