ive seen DKIM signed mails that did not have their key in DNS fail verification without being marked as spam by google. and i have (not) received mails because of failing spf validation made delivery fail silently so i think you are quite right in that regard at least for gmails interpretation of those signals...
Gmail has a blackbox ML that takes SPF and DKIM into account, but with a certain scoring that might not matter that much compared to said IPs reputation in their system.
