I've heard variations of "I want to follow directions so I don't piss off the agent" for most of my career.
I heard it recently again, as a writer wondered about nudging agents who hadn't responded to her query.
My answer to her was "so what if you do?"
It's not like the Query Police will rip your pen from your hand, purloin your furred writing companion, and throw you into the fiery pit of burning fiction novels forevermore.
If the agent is annoyed (and they should NOT be) all they'll do is kvetch and move on. Querying writers aren't anywhere near as annoying as publisher's royalty statements.
And the honest to Garamond truth is you won't piss the agent off.
The reason agents hammer on "follow the directions" is NOT "so you don't make me mad."
It's follow the directions so I get the info I need to assess your work, without a lot of other stuff to wade through.
When you send a query and start with a synopsis instead of the query, yes it's annoying. It's annoying cause you didn't follow the directions of "send the query; I don't want a synopsis."
It means I have to dig around in your email to find the actual query.
But I don't even remember your name or title past that.
There is no blacklist.
There is no fecal roster.
About the only way to get blocked on my email is to scare me or insult me.
Scare me: Let me know when I can come to your office to discuss my sure-to-be-a-bestseller book with you.
Scare me: I know a lot of people will be very unhappy if this book isn't published.
Insult me: I've queried hundreds of agents and you're all clueless gatekeepers who would have passed on Jane Austen too.
Insult me: I really don't want an agent but I’m told I have to have one.
All human interaction involves friction of some sort.
The trick is to be polite.
If you're following up on a query, just say that.
No need to apologize or explain, or beg leave.
All that Uriah Heep crap just takes up words, and the best follow up emails are SHORT.