EIP-7782 proposes to shorten the subslot durations, which increases bandwidth demands and raises the risk of network congestion and instability during peak usage, and would require extensive testing to avoid these issues.

Quotes that support claims

There could also be higher bandwidth demands from more frequent consensus messages and a greater potential for network congestion during peak usage periods. It would also need extensive testing to avoid network instability and breaking smart contracts.

Slower validators could struggle to keep up with tighter deadlines, bandwidth requirements could increase, and poorly tested changes could risk network instability.