I'd argue that 'miles offside', whilst it is an exaggeration (clearly), is more of an idiomatic expression than anything else and is so common, and not just in sport but many areas of life, that no-one can ever believe it is intended to be factually accurate.
Of course, it's obviously also true that no-one seriously thinks that it's necessary to 'forfeit your first born' to buy a season ticket. However, that isn't it a common idiom, so it's maybe, more like bringing Hitler into an argument over traffic wardens, ie, just a little over the top and not always the best way to make your point?