the last few years, it started working with Beta 2/3, without HSBC doing anything. One year, they did an app update and it started working inbetween new betas. So, sometimes it could be something they spot and fix that's not new iOS specific, but tangnetially sorts it.
I will do what I like, plus the app has started working in previous years with Beta 2 or 3.
You must be new around here. That's the standard spiel from a company. I've done Apple's beta's for many years. As mentioned above, in previous years it started working from the 2nd Beta, which meant it was something broken by Apple. Some years, when HSBC updated their app, it sorted it, meaning something unrelated to the new iOS caused the issue on the beta, that got fixed.
Basically, don't bother relying on what the company twitter says, as it's meaningless. Just standard blurb to cover their rear ends.