Yes. Tile and grout are the finish surface, and should not be relied on as the shower’s waterproofing system. The wall and shower-base assembly needs a suitable water-management system, with its joints, corners, drain connection and penetrations treated according to the chosen system’s instructions. A grout sealer is not a substitute for that assembly.
Before choosing finishes, ask which waterproofing system is proposed and how the wall, base and drain connect. Confirm how it will be checked before tile covers the work, including any water test required by the system or local authority. Keep the product and installation details with your project records. Review these construction details during design planning so the shower’s appearance and the assembly supporting it are considered together.