Temporary admission is the customs relief that allows a non-EU-flagged yacht, and the tender carried with it, to be used in EU waters for a limited period (typically 18 months) without triggering import VAT. It is distinct from being VAT-paid: the relief ends, and a formal import declaration converts it into a VAT and duty assessment on current market value.
Flag-shopping does not change a tender's VAT position, and the customs value at import is the value then, not the original price. The importing a yacht tender into the EU and UK guide covers the mechanics.