That's very interesting. I found a relevant thread on TMC[0] which seems to show that the two packs have the same part number. However, it didn't have a direct report of a software upgrade in a service center. Do you have a source?
It was on TMC somewhere. I couldn't locate the original message about the test drive car, although there are some mentions of that message. I did dig this up:
That's a report of a P90D owner in the UAE who got theirs upgraded to Ludicrous using just a laptop and an underline for the badge on the car. According to that, early P90Ds weren't this way, but newer ones are.
It is definitely weird. You'd think this hardware costs a lot of money. Maybe inconel contactors and pyrotechnic fuses are cheaper than I think.
Hm. Interesting. I can see a couple of other possibilities:
1) The upgraded hardware was required to support the current draw in the regular P90D, and the decision to offer the Ludicrous upgrade was an economic one.
2) The upgraded hardware was required to support the current draw in the regular P90D, but given their battery and drivetrain warranty they limited the max current to avoid excessive wear on the parts. The price of the Ludicrous mode upgrade is intended to offset increased maintenance costs while under warranty.
Those are both good possibilities. Another one that comes to mind is that the upgraded hardware isn't necessary and isn't particularly cheap, but isn't too expensive, and the ability to offer an easy post-purchase upgrade offsets it. For example, if the hardware costs $1,000 but 15% of P90D owners later upgrade their cars for $10,000, that's a win.
[0] https://teslamotorsclub.com/tmc/threads/p90d-insane-p90d-lud...