I'm a Mackem who has worked in Newcastle for over 5 years and have encountered this kind of bullshit opinion from Geordies over the years, it is regularly pushed as legitimate yet in reality has no real foundation. I do not know Newcastle well but have been asked for my trainers whilst meeting a friend in "Cow Gate" (yes, somebody in an undecipherable accent asked to have my trainers, or trainazz as he said).
Your accents are deploreable; with special emphasis on your double vowel sounds "ee" and "oo" which are unique to England (however can be found in Scotland), you almost pronounce them as an "i" and "u" respectively. If you look across other northern cities; Manchester, Leeds, Hull, Middlesbrough and yes Sunderland the vowels are lengthened (hence the two vowels) as they should be. Your pronunciation of words ending in "-ers" become the hilarious "-azz", you even throw a "y" sound into the word "here" = "hyerr". My personal favourite however is placing your guttural "u" sound where it doesn't belong, for example; The letters "Ur" together make the sound we can all make in words such as "Burn", "Hurt", "Work", "World" etc, however you decide to substitute this for a caveman grunt when it comes to; "Hurry", "Worry" and "Durham".
For clarity I supervise over a floor of more than 50 people, when i joined I'd estimate 80-90% of the floor were Geordies, over the years I've managed to get this down to around 50-60%.