It does ask, but often the Yay, thanks for changing my setting that I didn’t ask you to change button is much more prominent than the Wtf I didn’t ask for this put it back how it was button, so people think they’re being told rather than asked and just confirm it without realising they had a choice. Also, a lot of people just click the Next/OK button without reading and are surprised by the consequences. It’s not a major difference than just changing the setting of people don’t realise they’re being asked to opt in and can therefore opt out, but it is a bit of a difference.
A lot of the comments are making the assumption that the buttons are telling the truth about being different sizes, but I’ve flushed plenty of toilets where both buttons do a full flush. If you can’t tell the difference after experimenting, it might just be broken or cheap tat.