There are upgrades and there are upgrades.
Someone mentioned it already, Sony use 'A' to designate minor upgrades, and there's no press release. People find out about it is when they're no longer can find one without the 'A'. The only exception is RX100V; RX100VA gained a new processor, bigger buffer size, and there was still NO press release. With a new processor, there are new firmware with additional features. It did lose the PlayMemories Apps (allowed developers to develop in-camera apps).
I care less about the sensor but MUCH more about the processor which opens up many options and additional features. FYI, stacked sensors have less IQ (dynamic range) than non-stacked. Think about it before asking for one.
Don't know about Canon.
Sony A1 II has the same senor as I. It gained an AI processor and allowed better AF. Many people (bird photographers) I know upgrade from I to II. It's hard to get an A1 II in the States - first the demand and the tariff slowed down the shipment.
Nikon: people complain about the senor for its newer Z lines, but they upgraded the processor to the one used by the Z9, including the DX. Some suggested the recently released Z5II might cut into the higher spec Z6III sale, but the same people also think it's about gaining market share.