Hmmm.. Agree they can't show it, but they can most def. talk about parts of it, their role and show contrived examples, discuss language skills, architectural elements, improvements they wished they could have made, how they worked with others on the larger team, presentations they made... the list goes on.

This is especially possible given that a lot of work includes open source code, publicly available APIs, SDK services etc. In interviews I've conducted, when a candidate mentions these its an opportunity to dive into more detail on their expertise ..and again discuss contrived examples.

In addition, probationary periods are a way to guard against complete mismatches.