401 (k)Plan compensation exclusions

In our adoption agreement we exclude for deferral, match and employer discretionary contributions "all fringe benefits (cash and non-cash) . reimbursements or other expense allowances, moving expenses, deferred compensation, and welfare benefits.

I am new having just started in July and working with auditor- they have picked a sample who was paid short term disability for about half the year (2019) and are questioning why she did not get a match true-up. We are self insured and pay the employee STD through payroll. She did have  401(k) deferrals withheld on the STD pay and the plan was amended 1/1/2019 to exclude this from all plan contribution types;i.e 401(k), match and employer discretionary. The employer discretionary did include the STD pay for compensation purposes as well

What is meant by "welfare benefits"? Would employer paid STD pay be included in this welfare benefit exclusion? 

Much thanks!

Alexa

ps. 1 follow-up : we do exclude in another section of plan compensation "long term disability payments" but STD is not mentioned here