1) I see you are still clinging desperately to the "why" :-) It certainly looks like it was implemented to use a zero index.
2) Those frames have no delay specified. For frames that have no delay specified, different applications, sites, gif analyzers, etc. will return whatever default number they want. Some use a minimum of a 100ms delay to slow down the gif animation. mIRC will return zero because... no delay has been specified 👍
