Seattle, my guess would be that "PLS" has transitioned to ALS, as is frequently the case and can reportedly occur as late as 10-25 years after onset. Weakness and atrophy are minimal at worst in PLS, since only the upper motor neurons are affected. The extent of disability that you are describing would be associated with ALS rather than PLS.
If the EMG were repeated, it would likely show lower motor neuron damage this time. So this would be a good time to start tracking or keep reassessing breathing and swallowing, to consider BiPAP, a modified diet, and a feeding tube, if/as they are needed and agreed. I am assuming there is now a wheelchair, hospital bed and patient lift in use.
Best,
Laurie