You are both 100% correct! While this proposal addresses spam and quality control concerns, it does not remove the financial incentive if enough voting power wishes to pass as many governance proposals as possible.
If you read the Arguments Against/Potential Issues section of this post, under argument (2) I bring up your exact concern, and provide potential solutions. I favor solution 3 brought up in Community Discussion: Revise Governance Voting Rewards to Fix Proposal Spamming Rewards Exploit, which talks about fixing the governance rewards as a percentage of the overall voting rewards. This way, regardless if we have 0 or 1000 governance proposals that hit the NNS, the rewards payout is the same and both spammers and voters have no financial incentive to vote on spam proposals.
I chose not to include that in this proposal, as I feel that removing the financial incentive to pass spam proposals can be solved in a separate, but complementary proposal. There are many different ideas out there that tackle the financial incentives directly. I believe my idea to fixing the governance rewards over a week-long period will solve this issue, but it also received a decent amount of pushback and I believe it might be hard for the voters to digest such a big change all at once if the Incubation Period + Minimum Support threshold changes were tightly coupled with a change to Fix Governance Rewards.
Therefore, I want to continue gathering feedback from the community with respect to fixing governance rewards for the time being, and will later submit a distinct proposal that hopefully addresses these concerns. If you have any ideas/concerns regarding fixing the governance rewards and removing the financial incentives to vote on spam proposals, please leave those comments in Community Discussion: Revise Governance Voting Rewards to Fix Proposal Spamming Rewards Exploit.