A trip abroad of more than one year automatically voids your continuous residency, except for a very narrow category of exceptions such as US military service or US government employment. You do not have an opportunity to prove you intended to maintain continuous residency. It is automatically voided, unless you meet one of the exceptions.
A trip abroad of more than six months but less than one year may void your continuous residency unless you prove that you intended to maintain continuous residency, for example by maintaining ties to the USA such as home ownership, US employment, bank and financial accounts, tax filings, voter registration, vehicle registration, etc.
The difference is that a six month absence still leaves you with a chance to prove your residency. A one year absence is an automatic disqualification.
