Why Soviet facilities could not hide German submarine development

Could Germany have used Soviet facilities to develop submarines as it did for tanks?

No. The Soviet Union lacked the industrial base needed to build submarines, and the tank comparison does not necessarily apply to a naval program.

The question proposes moving German submarine development into the Soviet Union to conceal it from Britain. The required submarine-building industry did not exist there. Political cooperation could not substitute for specialised yards, equipment, and skilled production capacity. The familiar claim about Germany using Soviet facilities for tanks should not be stretched into a simple model for every weapons program. Naval rearmament leaves an industrial footprint that cannot be hidden merely by changing location.