ADA has a specific definition which is an impairment that significantly limits at least one of life's major activities - these are also defined. google it.
ADA provides for those with disability to get a "reasonable accommodation" if the accommodation doesn't cause the business "undue hardship" Not all conditions require remote work as an accommodation.
Yes all accommodations are being reviewed. if it doesn't meet the above criteria, back to the office you go - 3 days a week. Any days less than that is still considered an accommodation.
So to answer OP's question - nope, not discrimination if it doesn't meet ADA definition. If it does, WF keeps the accommodation active.