I did not consider it invalid. But there are legal firms online with articles and some agree with your comment and some do not.
Does the attorney first ask for re-inbursement for medical expenses and prescription medications up to the last date of treatment.
Receive a check for that and then communicate further on the rest?
The rest would include pain and suffering, estimation of future medical cost, etc.
I thought a demand letter would request a number and that number would include everything. (?)