Why larger carriers and LHDs face different length limits

Would the proposed carriers and amphibious ships grow beyond 375 or 410 metres?

No. About 300 to 350 metres is enough for carriers, while LHDs must stay short and manoeuvrable enough to operate close to shore.

The conventional carrier concept stops at roughly 300 metres, while 350 metres is ample even for a much larger design. Extra flight-deck length must justify the larger hull rather than becoming an end in itself. Landing helicopter docks face the opposite operational pressure because they must approach the coast. A ship expected to work in fjords or other confined waters cannot sacrifice manoeuvrability merely to maximise size.