You apparently don’t understand the issue. The problem was never the GPU.
the problem was caused by those WD Black and Seagate (I forget the model) 7200 HDDs. These caused excessive heating and cooling of the GPU putting stress on the solder joints. Baking reflows he solder which is why it has a good chance of working.
I take care of a large number of these for a school district. We replaced the HDDs and NVRAM batteries a few years ago on a schedule. The drives were likely to go bad after 5 years (100% had problems and could not be reused). Total number of those iMacs that developed GPU issues = 0. I’ll know in another year if any develop problems but I’m not expecting any. These machines won’t be retired till Apple discontinues security updates for High Sierra next year.
In 2012, Apple went to a cooler HDD in 2012 but those still had some issues. In 2013, they went to an even cooler, slower drive.
In any case, a 27” 2009–2011 with an SSD (preferably installed a few years ago) is a great machine as long as you don’t need to run Mojave. The 2011 has a SATA bus which gives it a minor performance edge over the 2009–2010. I also like that I don’t have to pull the motherboard in a 2011 to replace the battery.