For all I know it is a picture where the fuse was subjected to an overloaded condition beyond its’ ampere rating for a period of time.Believe what you want, next time you switch on a high current draw amp, see if you can see the resistive element inside the mains fuse move and bend a little.
That’s why in an amp with no problems, if the old mains fuse mysteriously blows, it’s 99.999% of the time at the switch on surge
Cheers George