133K is upper middle class??
Well, it is definitely a politically-loaded question... but it doesn't seem totally unreasonable, at least based on population percentages. They said "middle class" not "rich"; this is for a family of three, which nowadays means two incomes in the majority of cases; and $133K was chosen as the very bottom of the "upper middle class" window.
Pew is considered rather less politically biased than the Wall Street Journal; but in 2022 they gave the following broad-brush definitions for a family of three:
Lower-income (28% of US population): Under $56,600 per year
Middle-income (52% of US population): Between $56,600 and $169,800 per year
Upper-income (19% of US population): Above $169,800 per year
There are certainly a lot of political side questions one could ask, like - should we really consider it to be "middle-class" if a person can't afford to buy a house?