I agree almost completely with your explication of how SP, and curation rewards, work. However, I note your discussion doesn't much touch on the rewards pool, and I have understood that vesting does not inflate one's HODLings, but actually and contrarily, reduces their value over time. There is a separate savings mechanism that can provide interest, but SP is not that particular mechanism.

"To summarize, VESTS (remember that SP is an abstraction of VESTS) allow you to:"

"Earn passive income from STEEM inflation"
"Vote on content, proposals and witnesses"
"Acquire resource credits that are required to transact on the Steem blockchain"

So, in the above quote, the passive income isn't actually coming from SP itself, as the inflation of Steem is actually decreasing the relative value of SP, but is potential from the savings mechanism.

Active income is available both from curation and author rewards.

Otherwise, you have well elucidated my understanding.

Thanks!