Online deliverability test inaccurate because its not in the instantly campaign ?

Okay, have been posting a lot about it but basically despite warming up ALOT I still got deliverability issue when contacting deliverability testers online (mail reach), I would contact those using the instantly inboxes I bought there but using gmail to send the test email as instantly doesnt really have a feature to simply send emails without it being a whole campaign.

So every results I got from those test was really bad, but the deliverability test from instantly were good, but what if both were right ?

I spoke to instantly's service chat and they told me that "landing in spam from emails that are not from campaigns is not related to the infrastructure (regular or Pre-Warmed DFY accounts)."

So then is my email all good, all warmed up and only "bad" when I send tests on gmail but still very good with campaigns on instantly ? or is that totally dumb and does not make a difference ?

hope I'm not being confusing, this is all so annoying I literally just wanna start sending normally and im stuck at that.