While I referred datasheetTPSM53602RDAR, as the switching frequency is dependent on the input voltage, output voltage and the load current.
Most probably we might be at 1.4Mhz switching freq in PWM mode for the cases only if we hit the min load current per figure 7-14, 7-15.
TPSM53602, 3.8-V to 36-V Input, 1-V to 7-V Output, 2-A Power Module datasheet (Rev. B) (ti.com)
what might be the switching frequency, where the load currents are lower, which means the part would be in PFM mode