I agree this cohort have been affected by Covid, and the lack of GCSEs were a major issue for them.
However...
All schools know about the pegging to 2019, and have known for quite a long time. Certainly this year in all exams, including mocks, we've used 2019 grade boundaries. Beyond this, we've been marking to the mark schemes as we always do- there's no "marking to 2019 standards vs marking to 2020 starndards" in my subject anyway.
To be honest, 2019 grade boundaries are the last set of useable grade boundaries for most subjects- it's not fair to mark against 2022 grade boundaries, due to the advanced information given, and the cohorts who actually sat November exams in 2020 and 21 are too small to give useable grade boundaries.
If your school hasn't been doing this (although I doubt it) then it's fair enough to be concerned, but teachers have known about this for a long time, and have been using it to inform their assessments, yes...
In terms of predicted grades, I would argue that every school is at least slightly optimistic in their predictions- we assume every student will have a good day during their exams. We don't predict things that are completely unrealistic, and we are cautious in terms of predicting A star grades, but there's no value in giving students pessimistic predictions.
Unis know this, and they also know about covid, and lack of exams and all the rest of it- they'll have made their offers in this context.
I'm sorry if this is genuinely news to you, but it's not a decision that's just been made and it won't be news to the school. I know it's a really stressful time, but this shouldn't be a cause of worry to you.