TL/DR: this is "github runners as a service", and claimed build time improvement appears because they OpenFire gives more CPU/RAM resources that default Github runners. I guess a good idea if you rely on github's default runners... but if you are already using your own runners the benefit may or may not appear. For example hosting runners on EC2 is 2x cheaper, and gives you stuff like shared cache.
Also, "just change 1 line of code" is a bit of exaggeration.. It is more like "sign up with Open Fire, enter your credit card, grant them access to all your git repos, change 1 line of code, don't forget to pay the bills".
Also, "just change 1 line of code" is a bit of exaggeration.. It is more like "sign up with Open Fire, enter your credit card, grant them access to all your git repos, change 1 line of code, don't forget to pay the bills".