iOS is meant to use whatever it can at any given moment for location, being cells, Waps, Bluetooth, or GPS.
WiFi does support time of flight in some measure. My iMac uses it in deciding whether to allow my watch to unlock it, based on actual distance (8 feet, I think), rather than assuming anything about signal strength. Car manufacturers with their flawed keyless entry systems, that are easily spoofed by signal boosters, could learn from that, but that would be another thread.
But I do not know whether iOS location uses time of flight to ascertain Wap distances. Another recent thread, we speculated that iOS might need at least two consistent Waps within earshot, before trusting location, as a single Wap might have moved since its location was last known. Just speculation though, I’ve never seen anything definitive pubslished by Apple.
Iphone should be able to use GPS, which would obviously trump WiFi or cell towers for accuracy. But for some reason it has been spectacularly unreliable for the past few iOS versions. When tracking better half, her location can be several miles adrift, even in open air under a clear blue sky. It’ll suddenly improve (accurate to feet) if she unlocks her phone, but that should not be necessary.
I have tried long and hard to figure out a way of getting around that GPS bug of last paragraph, so I can track her properly, but never succeeded. It used to work and my old iPhone 5c, stuck at iOS 10, seems much more reliable.