3: it's already all set-up with the right conectors so no need to mess around with adaptors to connect your test gear to the device under test.
That is the problem with most PAT machines it requires a host of adaptors to be carried around with it to allow connection. Mine has an IEC C14 plug but to test IEC C6 clover leaf required an adaptor, same with C16A, C20 and C22.
As to phone chargers there are so many connectors and even if you can connect one has no idea as to what damage may be done by testing isolation. Be it testing earth leakage with 500 volt or testing class II with 2500 volt there is always a risk that the test can cause damage.
Today the 2500 volt test is reserved for repaired equipment before returning to service to test in case any screw is too long and would only be used by the repairer so he would be aware of any items likely to be damaged.
I accept with a 500 volt insulation resistance test modern equipment should be able to withstand the test on the low voltage side however I would still use leakage current only on IT equipment.
To use extra low voltage to prove isolation is of course useless but also to test with 500 volt between the extra low voltage output of a switched mode supply and the low voltage input is really asking for trouble.
The point is not only may it cause damage it could also stress components causing them to fail at a latter date so instead of the test ensuring safety it could actually cause a hazard.
To me using even 250 volt between an USB connector and a mains plugs pins is crazy.
Basic way a switch mode power supply is AC to DC then back to AC at high frequency and transformed down. So far so good but then the next step is to sample the DC output and alter the mark/space ratio of the DC to AC bit to control the voltage this return link may have enough of a capacitive or inductive link to be damaged by testing for isolation.
I would be interested to see if anyone other than "plugwash" sticks even 250 volt between the ELV and LV connections of a switched mode supply as part of a standard PAT inspection.