I have a Mac Pro 5,1 and I installed a HL-DT-ST BD-DVD RW GGC-H20L so that I can rip Blu-rays and HD-DVDs and it works wonderfully! I have been able to get quite a few HD-DVDs for cheap due to people thinking that they're completely useless AND they're not!
So if anyone is wondering if MakeMKV works with HD-DVDs, it still absolutely does and I am very glad about that.