Thats not completly right at least under german law (and most likely also under us law).

A license is basically a contract between you and the copyright owner. If the copyright owner changes the distribution of a piece of software to a new license you have a diffrent contract with them. So you have to hold up this new license. If you already had a license (in this case gpl) you can use this old contract, but you can not download a new copy delete what was added since the copyright change and use that under gpl. You would have to proof that you had the gpl license before or in this case that it got relicensed to you.

So the original code wasnt gpl at all then. If this was true i would be pretty sure this repo would already be closed.

No, this is plainly wrong. A license is a proclamation of the copyrightowner how others can use their material. The copywrite owner does not license their own work to themself, they can do whatever they want with their copyright. If you are not the copyright owner you have to have the license and afe only permitted to use the material after that license.

Well yes and no you can release them going forward under a new licence. If you obtained your copy under the old license you can use it under the old license when you obtain a new copy you have a new license agreement. Thats absolutly possible to do.

Revoking licenses is alot harder though and changing the lizens from a foss on to another is often confusing and business inapropiate. However it is legal.

Edit: A license is for not vopyright owners not the copyright holder. The copyright holder can basically do whatever they want.

Well yes and no you can release them going forward under a new licence. If you obtained your copy under the old license you can use it under the old license when you obtain a new copy you have a new license agreement. Thats absolutly possible to do. Revoking licenses is alot harder though and changing the lizens from a foss on to another is often confusing and business inapropiate. However it is legal.

If you are the copyright owner you can relicense any way you want learn some copyright law.

Very broken gears