Cool, thats a different claim than what you said above but at least one I can actually engage with.
I've run linux on many Dell and Lenovo systems over the last 25 years. Most of those systems were fully unsupported by the manufactures for anything but windows. And yet, random people on the internet contributed to make that hardware (mostly) work. I've not seen any particular improvement in the driver situation since Dell started selling linux certified systems.
Its not really surprising though, Dell is just an integrator. All they do for their systems with linux pre-installed is to pick hardware that already has drivers. They took a little bit of work out of needing to research if a given configuration is likely to work or not with linux (which is good). They don't really deserve much credit beyond that.
Its also a little funny because most drivers from hardware manufacturers suck. I don't know why, but most hardware companies are terrible at writing software. Its easy to list off hardware companies that have a long history of shipping mediocre, buggy linux drivers: nvidia, amd, broadcom, realtek, (maybe i should just list every nic and wireless chipset manufacturer). Some of these companies have gotten better and have learned how to be good kernel contributors, but they were mostly bad for years and years. Thankfully in some of those cases random people on the internet reverse engineered the hardware and contributed from scratch drivers to the kernel. Most of the time I've been happier with the experience of running those from scratch drivers than what hardware manufactures ship.