DMARC is an anti-impersonation standard, not anti-spam.
DMARC alignment is trivial to set up, so even spammers can do that. That, amongst other reasons, is why all major spam filters are based on content, not DMARC alignment. This is why you can have 100% DMARC alignment and still end up in spam.
Failing to meet DMARC alignment will result in your email being marked as suspicious (with a big fat warning), or flat-out rejected (not delivered), but it typically won't be marked as spam (unless content is flagged as spam, of course). What exactly happens on DMARC unalignment somewhat depends on your DMARC policy, but mostly on the policies/implementation of the receiving provider. Each provider handles DMARC unalignment different.
One thing that is consistent, is that none of the email providers will reflect in any way if your email is flagged as spam or not. Otherwise spammers could trivially figure out which content trigger spam filters, and which content won't. A DMARC report will not tell you if your email is flagged as spam or not. This is also why most email providers will always fetch and cache tracking pixels, again to not expose to a potential spammer if their content made it into an inbox or not. This behavior makes it look like every receiver has opened the email, even though it never happened. This makes tracking pixels useless.
So, Resend's claim to show you 'all the events' means they can display how many mails were send, how many have bounced (due to various reasons, except spam), and how many tracking pixels were loaded. But as explained, the number of pixels loaded does not, in any reliable way, reflect the number of emails actually making it to the recipient's inbox.
Reliably sending email is an insanely hard, you can never guarantee delivery with email anyway. If the 'React' email template editor is the novelty in Resend, I'd suggest them using something like SES to actually send the email. Don't try this yourself, until you verified your product-market-fit and have the scale to invest (heavily) in your own delivery network.