If you have a meta point, and it is set to log all data. You set it a value, and nothing else sets a value, no update events occur for the meta point. You restart Mango. Yes it should have the value you set to it.
You could have other properties get in the way, but I would be surprised had you set them up as such. Some things to be aware of:
If you meta point is interval logging then until that interval log, there is data that could in theory be lost. The interval should begin either when the data source is enabled (if polling, or at next poll) or when the point is enabled (if not a polling data source, like Meta). So, if it's a minute average and Mango loses power 59s into that interval, that data is lost.
There are prevent extreme sets settings that will prevent it from setting a new value outside those bounds. These are disabled by default.
There are prevent extreme values settings that will prevent it from logging extreme values. This is astronomically large values by default, and also disabled.
All that to say that if you're on the Data Point Details page and you toggle "Show cached data" off, then all the samples in that table are recorded in the database and will persist through a power cycle.