Well I believe it CAN be true, but no way of knowing if he actually opened it on a regular basis or not unless you take his word for it.
There are several examples of sealed Eco systems out there, often times during Christmas time you will see these, on sale at amazon was on debated on TPT a few times:
Which are often debated because they contain live shrimp, and even though the company says they do not harvest their shrimp from the wild, I have read some pretty convincing information that states otherwise.
I can see this happening. Plants and life in general will do its best to survive under most conditions. With the right balance of life in the compost, food from the plant, co2/o2 production, and light, I don't see why this wouldn't work, aside from anerobic conditions in the soil.
Not impossible, just highly improbable. Gotta' figure out of the hundreds of thousands of such set ups created over the decades, at least a few will be well enough balanced to survive a lengthy period with proper care--there might not be water and ferts going in, but temps and light levels are still active variables.