I think that this is the result of a KPI.

At some point there was a fight inside Google between engineering and marketing about how to proceed with product development. Engineers wanted a better product, marketing wanted more eyeballs.

As a result, search became about “engagement”, or “Moar clicks is betterer”.

Seen in this light, your triggering of the assistant four times increased your use and thus your engagement. An engineer would point out that this is not a valid metric, but Google is now run by the marketing and accounting departments, not by engineers.

Another aspect that I only recently became aware of is that in order to get promoted, you need to make a global impact. This is why shit is changing for no particular reason or benefit and has been for a decade or so.