Hi Mark,
There’s been no changes regarding this. The feature is possible and we want to build it, but we don’t have defined yet when we’ll work on it.
The current UI control is still shown so you can resize the stack item: shape, symbol or stack, proportionally (or not). This lock control does not have an effect when you resize the parent stack, which is the desired effect. And I can clearly see how that piece of UI is confusing when working with stacks.
The only current way to resize with the same aspect ratio is to use the Scale tool (K). You can also try the method described in this topic, but you’ll see some differences in sizing.