I wouldn't worry about the "non-salaried" exclusion. UKVCAS processing is reasonable and if they can see your application is bona fida i.e. not fraudulent they will ask you for more info if something is missing.
The ‘non-salaried’ part is very important and needs to be on the letter.
If the employer letter does not explicitly state that the position is NON-salaried, then UKVI may use the salaried calculation (lowest payslip x either 6 or 12 months) instead to calculate the income requirement.
We had someone who had their visa refused a few years ago specifically because of this… they met the non-salaried requirement but their employer letter did not state this, so UKVI assumed they were salaried, used the wrong calculation and incorrectly refused the visa. They had to go through a whole process to get the decision overturned and the visa approved.
Because of this, we now advise that non-salaried income is very clearly stated as part of the application.
Sent from my iPhone using Tapatalk