I believe calculating mwh for their battery as 200mAh * 3.7V is not very correct, because lithium battery voltage drops to 2.8V at end of discharge, and at beginning it is ~4.2V. But it is hard to find, what are curve of lipo discharge at such low discharge rates, looking to 0.2C capacity and approximating, capacity might be even higher than expected! BLE will draw almost 0.5C, which is reducing capacity, but i believe it wont be significant difference, because LiPo is quite good with high discharge currents. So approx it might be correct, but interesting to know what are more precise values.

Also for LiPo self-discharge is 5%, so we need to compensate approx 37mWh monthly(1.23mWh/daily), but if as stated it generates only 1.25mWh/day, we just getting very close to be out of juice, because of self-discharge!

Another thing, for example CR2032 with 3.0V fully charged to 2.0V end of discharge, with their 230mah, is just 645mW(dave took 600mW, which is very real). If we calculate as with LiPo, with 3.0V it should be 690mW, but seems real "average" voltage on discharge curve is 2.83V. It can be seen on discharge curve:

P.S. I had really serious issues with CR2032, because at 1beacon/sec rate with BLE, with such battery intolerance to high currents, it lasts much less than expected, because battery vendors specify 230mah for very low discharge current.