Short answer
Yes, it's wise to prevent access. Erythritol can cause diarrhea and gas in dogs, so store it securely in a high cabinet. You can also train a solid 'leave it' command for extra safety. Watch for signs of an upset stomach if he does get into any, and call your vet if you see vomiting or severe diarrhea.
Erythritol — Food safety facts
Feed with care · Dogs · full breakdown on the linked food page
A sugar alcohol that causes diarrhoea and gas. Do not confuse it with xylitol — that one is toxic.
The full verdict, portion guidance and serving notes are collected on the Erythritol food facts page.