Disregarding 8 radar antennas with 360 degree coverage instead of one,
Yes, because that idea is nonsense. We know that the SU-57 has a central nose radar and two cheek arrays. Where are these other putative arrays supposed to even be on the aircraft?
There are AESA arrays in the leading edges of the wing, behind the slats, yes, but those aren't radars. At least not primarily. They couldn't be; they operate in too long of a wavelength and they are simply too small to have adequate resolution. Those wing arrays are LPI IFF, with a secondary role as jammers.
The tailcone? Maybe there's a radar back there, but what exactly would it do? Again, radars are sized they way they are sized because of fundamental constraints of physics. Anything that small is going to have poor range, poor resolution, or both. The only thing it would be useful for is a MAWS, but that seems unlikely because we already know that the SU-57 has a UV-based MAWS with distributed, hexagonal apertures all over the airframe.
Any phased array RF emitter on the SU-57 that isn't the main nose radar or the cheek arrays is probably a jammer first and foremost. They're too small to be very useful radars. I concede that if they are all AESA then it wouldn't be terribly hard to use them as radars if the need arose, but what could they possibly be useful for?
MUCH better speed and all-overall agility even with current engines,
I think that the SU-57 is faster than the F-35 because it has variable geometry air intakes. Those aren't really a net positive until around mach 2.0, so it seems reasonable to surmise that the SU-57's top dash speed is somewhere north of that.
But better overall agility? Really? Tell me how you determined that. I suppose that you have access to TsAGI wind tunnel test results so you know all the details of the drag polar of the SU-57. On top of that I suppose that you spoke with NPO Saturn and they helpfully provided you with a chart of the dynamic thrust and pressure recovery of the engine/intake combination. And, needless to say, you also are privy to all the flight testing documents and know what the maximum AOA is as well as what the exact gross weight of the aircraft is with a combat load.
I further assume that you have the equivalent information on hand for the F-35.
Because that is the information you would need to draw up a set of E-M diagrams for the aircraft, and that is the bare minimum of information you would need in order for that statement to have any meaning.