In the beginning, those Swapping exchanges provide that rate for some pairs that are new just to get users to contribute to the liquidity(which would be low since not many provide liquidity to new crypto in those exchanges) So they have to set high APR rates specifically for those.
In my experience I used Apeswap and there was an Alt whose APR return was over 1500%, Then it came down slowly to 300% and then under 300% after the liquidity was enough.
I didn't use that function because I didn't trust to invest in a new volatile altcoin so I just witnessed it.
So at last, Those returns seem good but they aren't the same for every coin in the market, It fluctuates based on many variables and obviously it's good to provide liquidity on a good Swap exchange rather than a new one.
However it is also wise to remember that you are not getting those returns exactly, you know why? Because both the APR is changing like you said, but also price changes constantly as well, you are not going to get that return in dollar value and you are not getting it in cake (or whichever swap) or even in bitcoin.
Basically it is not a number that can be trusted, it is a random number at that point, doesn't matter what it says, doesn't matter if it is 80% or if it is 800% because in the end it could change overnight. How? Well you could do bnb-cake on pancake and get a very very tiny return compared to most, but then both bnb and cake could increase like hell and you would make A LOT more than any other pair. At the same time you could invest into something brand new and it would drop so much that you would have basically nothing in the end. So, it is never important to look at those APR numbers.