It’s unclear what time period is being referenced here. But I imagine it was not during the time when Opteron CPUs were leading the market, because IBM agreed to “sell” their fabs to GlobalFoundries Q4 2014 and Opteron had been steadily losing market share for 8 years at that point and had less than one percent of the server revenue from what I can find. As for AMD’s Radeon GPUs, they were produced at TSMC until the 400 series in June of 2016, going all the way back to before AMD bought ATI. That means that AMD never produced the Radeon chips at their own fabs before they spun off Global Foundries and didn’t put their Radeon GPU production on GlobalFoundries until the 14nm FINFET process. That 14nm process was one licensed from Samsung to replace GloFlo’s own 14 nm process that they canceled. It is safe to say that the reason AMD didn’t move Radeon to GlobalFoundries is because they didn’t want to and didn’t have to per the wafer supply agreement in place with GloFlo at the time (since AMD didn’t produce Radeon chips on those fabs to begin with). TSMC’s 28 nm was out well before GlobalFoundries had volume 28 nm production.

Here are some quotes from a semiwiki.com article from 2014 regarding the licensing of Samsung’s 14nm by GloFlo https://semiwiki.com/semiconductor-manufacturers/globalfoundries/3362-globalfoundries-gets-a-14nm-process/:

“I think this is really big news. GF has only recently started to really ramp 28nm which means that TSMC had a free run for a couple of years and was really the only game in town for most people (yes, Apple manufactured at Samsung but the average customer isn’t going to get Sammy’s attention). This meant that there was no price competition at 28nm plus a lot of systemic risk when only one company is building so much (if one of their fabs was damaged in an earthquake or a fire, for example).”

“The reason that this is such a big deal is that, based on their performance at 28nm, GlobalFoundries was uncompetitive, too late to market to get more than the crumbs from TSMC’s table. Any semiconductor company only makes money if its fabs are close to full and theirs was not. If they didn’t get competitive by 14nm then the future of the company was dubious. Abu Dhubious.”