If user submits the proposal during the sync process through the new Governance GUI, it will get accepted by the network, but the cycle will start counting from the moment (superblock) when the proposal was submitted. For example, if one cycle on testnet is 144 blocks, and user submits the 6-cycle proposal at the moment when wallet is still syncing and has 500 blocks left till it's 100% synced, proposal submission will be successful, but once the wallet sync 100%, that proposal will show 3 of 6 months left. It means that the proposal can be submitted during some of the already passed superblocks.