There are likely members who are transacting with their bitcoin, and they can transact directly onchain or maybe they use a lightning wallet.
I doubt that it is a good idea for guys to be getting scared away from transacting with bitcoin in the real world, when there are opportunities to do so. A lot of the power of bitcoin comes from being able to transact directly with other people and with no one being able to stop such transaction.
So even if their main storage of bitcoin might be kept separately and private, there could be situations where guys are either transacting with large transactions or guys might be using a wallet that has a high BTC balance, and even if the amount transacted might not be large, the balance of the change can be seen.. ... so if a guy might be buying some good or service worth a few hundred dollars, yet he is using a wallet with several thousand dollars, then the person who is engaged on the other side of the transaction may well see the change address...so it seems that some of us are suggesting to use wallets (or addresses) that have lower amounts of BTC contained in them or perhaps using lightning network, it might be more difficult to see the quantity of bitcoin in the originating wallet address.
On-chain transfer is good for p2p transfer (between two persons) and if you want to pay to merchant then best possible way is to use LN because on-chain will take lots of time for transaction to settle and both client and merchant don't want to wait for longer duration.
It's possible to hide you original balance as you have explained. It looks like the issue of kidnapping we have seen so far is not because of linking Bitcoin wallet balance with person's identity but because of person own disclosure about number of bitcoin's or other digital asset he has. These days there are many Bitcoin influencer's on social media that show there wealth to attract more likes and views.