Yes, it's mandatory. We don't start a build engagement without it, and we won't. The reason is simple: we have watched enough projects fail because they skipped the strategic foundation that we no longer take that risk on either side. Every brand we have launched in China successfully went through Strategy and Audit first, even when they thought they already knew what they wanted. About a third of those clients came in convinced they needed one thing, and walked out with a different plan that worked. The other two thirds had their assumptions confirmed, but with the dependencies sequenced properly, the budget realistic, and the compliance work scoped before it became a blocker.
If a different agency tells you they can skip strategy and go straight to build, you are buying their assumption that your situation matches the last project they did. Sometimes that works. More often it doesn't, and the cost of finding out is months of rework.