I've tailgated in to apartments loads of times before a booking, i've never had a WG complain about it once.
If you've got a booking confirmed & you're arriving at the agreed time what's the problem?
And yeah, it's the "bye bye" that really smacks of arrogance.
I got complained once by an SP as I'd texted her to say I'd arrived and she told me to buzz but as I approached the door to her building a load of residents turned up and I tailgated them as it would look weird if I didn't. I made out that the lift was too full and waited for the next one, so I'd go to her floor on my own. I arrived on her floor and walked to the door as usual and she let me in and then got complained at me for not buzzing. It turns out she uses the buzz in to get ready by her door, so you don't end up lurking around on her floor for her neighbours to see. She knows how long it takes to travel from ground floor to her door and she stands by the door listening for your foot steps. As I'd not buzzed in she wasn't standing behind the door, so there was an extra 30 seconds or so of me standing outside her door. Next time I visited her I made sure to buzz in and got no complaints.
On this one it looks like there are lessons to be learned on both sides. It does look like the OP followed all the rules. It might be that he got buzzed in by someone else by accident and that led to the following confusion. Who really knows

. It would have been nice if she'd accepted that an honest no harm done mistake had been made and gone ahead with the booking, but it's her rules as she has to feel safe. I wouldn't want to see an SP if she felt unsafe.