Some flaws with the analysis.
1) Difficulty couldn't go below 1 & the "network" has no idea what the hashing power is. We can only guesstimate the hashing power based on the time between blocks. If you look at the period of time between blocks in the first year you will notice there is variance. Variance can either be natural variance from the mining process or changes in hashing power. It is simply a false statement to claim the hashrate was a constant 7 MH/s. There is no way to prove that is true and it arguably never was. The spreadsheet is merely a guesstimate at an aproximate hashrate based on the average time between blocks of the preceding period and is subject to error like any hashrate estimate (i.e the times between blocks was X and since the AVERAGE block requires 4.2 billion hashes the hashrate would need to be ~y to solve block at this rate ON AVERAGE).
But a single computer in 2009 could do 2^32 hashes in 10 minutes. So if we assume that Satoshi PC was all time powered on mining, then we MUST accept that almost all the coins were generated by him. Why would Satoshi turn off his PC if he foresaw the future?
The average number of zeros in block hashes in that range is 33, not more. The average number of zeros in the first 30 blocks is 32.8.
We must accept that during the first two hours he was mining alone!
Therefore there was, at average, a single or maybe two PC mining (but rarely) until block 36288.So your argument is flawed
Please try to refute this argument!
2) There is no evidence that Satoshi mined alone the entire time. Hal Finney reports mining early (in the first 100 or so blocks) and there are other reports of people mining on and off during the early mailing list days.
My prior argument says exactly that: IF he was continuously mining, then he was mining almost alone.
When Satoshi announced Bitcoin on the cryptography....I mined block 70-something...
Everybody read that Hal mined the block 70-something, which means that he mined very little, as most of the people in that time interval.
3) The early client "mined" automatically in the background when running. For Satoshi to have mined all the blocks for the first year that would mean nobody, not a single person ever downloaded the client which is simply false.
People downloaded the software, mined a few blocks, and dumped it. Almost everybody except for Satoshi.
So again, IF he was mining continuously in that interval, then he has at least 500k BTC now, with independence if somebody else was mining or not.