>> list/collection of clients be called clients

I think it depends on how you say it, Charles.
One might say the client table - a place where any one client record would reside, just as one might say a guest house, a stamp collection, a bird house or a dessert table (to mix metaphors).
Someone else might say a table of clients, a collection of stamps, or a table of desserts and that person would probably call the table clients.
Some verbaculars don't use abstract nouns or collective nouns the way we do in most parts of the US.
So my wife, whose family spoke German (Schwabish) primarily when she was young says things like " two insurances" when referring to two insurance policies or "two breads" when referring to two loaves of bread.
She'd call it clients for sure.
I note that .NET "pluralizes" table names on its own volition in some cases and that drives me batty.