Names stick, it’s as simple as that. In most practical situations (such as this discussion), the distinction between Google and Alphabet doesn’t matter.
I once tried to rebrand an in-house, purely dev facing product. I failed.
I'm a heavy user of Google Chat at work. Whenever I encounter a space with in-line threading, I ask the others if we can switch to the topical structure (with separate threads grouped together and brought to the bottom for new messages, but no in-line replies). Usually everyone agrees.
If in-line replies become the only option, I'll have the choice of wasting countless time to dig through past replies, or just stop checking chat altogether.
I once tried to rebrand an in-house, purely dev facing product. I failed.