While that "rule of thumb" might have some relevance to signal level components, BK themselves clarify this in the text:
Measurement frequency: Since the reactance is a function of frequency, your choice of measurement frequency should reflect the usage of the component. For capacitors, larger values (tens to hundreds of μF or more) are often used in power supply filtering applications, so should be tested at twice the line frequency. Smaller capacitors (fractions of a µF) tend to be used at higher frequencies, so should be tested at 1kHz or more.
In the case of SMPSs the 'line', ie. switching frequency is normally 50kHz or more, so their words are completely in line with 100kHz testing of these higher capacitance parts.
You can't simply rely on that straight line graph without paying attention to the accompanying text.
The trouble is, these days, there are
several "rules of thumb". A capacitor with, say, 0.5R may be perfectly fine for a gentle rectified mains transformer based supply, it would be totally ineffective (Faulty) in an SMPS application with high frequency, high peak currents.
Sadly there is no non-application-specific simple single rule of thumb.