Elite Plus added only 2 miles to my overall plan and reduced my marathon pace by 5 seconds/mile

I am halfway through my marathon plan for NYC and am running a 10 mile "race" in 3 weeks. I don't plan to race the race because I have a 17 miler that weekend (and planned to tackle an extra 7 on after said race to complete that run).

I have done a B race before where I had set it up to actually race (although that's a different story-- Runna then put a half marathon practice run 2 days before the 10k, so I don't think that worked as intended), and I was just curious what Runna would suggest if I said I wanted to incorporate this 10 Miler into my training without pushing. I figured I could test it out and just remove it after and my plan would return to normal. Spoiler: I figured wrong.

Adding the 10 miler at the easiest pace of a B race shaved 30 miles off my total training plan. I immediately deleted it, and my total mileage almost reverted, but it was about 4 miles less than original, so obviously something changed. I had been thinking of going to/checking out elite plus soon anyway for additional mileage (I'm already running a bit more on a weekly basis anyway because my overall mileage feels light), so I enabled it and it added... about 2 miles to my overall plan. It also dropped my goal marathon pace from 8:20 to 8:25.

I am already lightly concerned/frustrated because Runna AI thinks I haven't been meeting my paces on multiple runs because I tweaked them slightly (ie, warming up for 2 miles instead of 1.5, but still doing the speed intervals as directed), and when I've run on the treadmill, I guess I added laps wrong, so it would basically see my extra warm up distance as not meeting a pace target, even though if a human was looking at the splits, it would be extremely obvious that I did the workout as intended, and I almost always exceed the pace targets. I think I haven't reached a target pace on maybe a single rep of a single workout in my entire training block (and there are only a handful of the misaligned treadmill workouts anyway). I recently (but before adding and then removing the B race) got a notification suggesting I should aim for a slower marathon pace because I have been "struggling to meet my paces". I declined the suggestion because I know that's not accurate, but that might have something to do with the new pace? Even though I declined and have continued to hit targets?

I know it's just an app, and I can control what I run, but I really thrive on following a plan, and i also don't want to over-add runs on my own.

I really like Runna but I am just confused and want to trust my plan is accurate/best for me!

Additional context:

Been a distance runner for 25 years but typically haven't exceeded half marathon distances before this training block. I also had a severe ankle sprain last December and ran a little bit in the early spring before going back to PT, so I was starting with pretty much no recent base in May. I did a month of walk-runs etc and easing back to running up to a (slow) 10k before starting the marathon plan. I'm 35/F, ran a 47:30 10k last week on a pretty hilly/tough course. Total marathon plan mileage right now is 610 miles over 21 weeks.

This ended up being a long post but... I guess I'm just wondering why my pace went down, what the point of elite plus is, and how I can add a bit more mileage to my actual plan?

Sorry for the rambling! Maybe this is all to say... adding B races have not worked out for me.