You're somewhat right with that comment. Most is not true, just some, actually few in the big picture of NES and SNES era games (Sega, included) did NOT use a battery. They didn't want to pony up the extra dollar for a CR2032 or like battery, nor did they want to pay more bucks for a SRAM bank that needed the battery to hold the information. Carts up until the mid/late N64 days and the GBA era did not use FlashRAM nor did they use EEPROM so they all relied on batteries. Since those cost money some developers who were notoriously cheap assholes, Konami was KING of them, refused to pop for a battery in this country well into the GBA days. All their N64, most GBA if not all, and anything prior used passwords when in their own country you could get a battery. Castlevania I feel for me was the worst as I knew in Japan not one of them used that aggravating picture based save grid, none of them.
You're right the N64 memory pack was essentially meant for transferring saves, large storage (Mario kart ghost data) and other impractical stuff into small chips within the games. Sadly, jerkwads like Konami used it to save a buck. Check the game list online for those who used the memory pack, Konami will popular on that list among a few other tightwads as well.