Many testing agencies and/or international marketing laws for electric appliances require you to specify either the worst case, being inrush or hiccup, current, or fully specify the current drains, powers and power factors.
In quite a few cases, in fact, you are required to specify the limiting current (either as an extra line, or as the number if you have only one line), which can be a "by design cannot draw more than" current, or can be the current at which an internal fusing element will blow.
Add to that cautious component maths around the power factor of ringing core transformers at varying loads and input voltages and >=300% peak currents surprise me not at all.
Apart from that, under-estimating the peak current will mean you fail random tests, over-estimating peak currents of small appliances costs you nothing. As long as you stay under an input power of 50W (and likely even 100W) rated the rules will be the same almost all over the world for a certain device and design. Regardless of whether below 50W means 10W or 40W. So why not estimate a worst case scenario of 25W or 40W, if it means you always pass the requisite tests and have to change nothing about the design anyway?
Concluding with the personal experience that a well designed small ringing core can be made to function at upward of 90% efficiency with a no-load/null power of (much) less than 300mW, I wouldn't lose too much sleep over your power bill.