Are all 'prospects' always 'potential' by their nature?

Solution 1:

A prospect that is potential is potentially pleonastic.

That is, it is a fine distinction that works if in context there are potential prospects and actual prospects, but outside of any context, all prospects are potential.

Is the idea of 'potential' necessarily part of 'prospect'? No, but it does invoke some quizzical 'Isn't that already potential?'.

If you look at definitions of 'prospect' (where definitions aren't authorities, but are well-studied attempts at capturing meaning in other words), they all mention something having to do with future events. And the future is, implicatively, all potential.

If your boss makes a distinction between potential sales prospects and actual ones, then it's not redundant. Otherwise, 'potential' will be taken as already understood in 'prospect'.

Solution 2:

While a prospect is a potential customer/client/buyer, a potential prospect is not yet at that stage:

There are two types of prospects; those that have an identified a need and are therefore potential buyers, and potential prospects who may or may not be viable. Usually you start with potential prospects, prospects that use or could use your product or service, but have no identified need. Through a series of questions, you narrow down the field to true prospects, a percentage you will convert to buyers. — James J. Kolins, Salesman to Superstar: Out Sell, Out Close, Out Earn Your Competition!, 2013.

Potential prospects can also be called leads:

Qualifying is the process that allows you to find out whether a lead is actually a prospect. A prospect is someone who has the potential to become a customer. Leads, on the other hand, are just potential prospects. If you don't qualify a lead, you may be wasting your time with someone who literally can't buy from you. — Wendy Connock, “What Is Qualifying?” BalanceCareers.com, 2 Dec. 2018.

Using the term potential prospects is thus not a tautology and makes a valid distinction between potential and actual prospects who may buy/contract for your goods or services.