PCpartpicker is warning you about potential issues if you assemble your PC without modifying the BIOS settings. All components are brand new.
Usually this alert indicates the system won't start unless you upgrade the BIOS first. Yes, skipping any BIOS changes means it won't function properly.
Batch 1 assumes the current board version. New updates will be shipped with the latest BIOS.
You can check the latest BIOS updates directly from the manufacturer's website or use tools like Windows Update to ensure your system is current.
Previous knowledge indicates you shouldn't rely on it. Frequently, these updates are missing, or the final release was finished before the BIOS change was applied.
Additionally, if the board includes an early BIOS revision, you'll need a compatible chip to install it, since updates require a valid chip. (Except for some premium boards that have their own dedicated flash button—rare.) Overall, this stage is late enough in development so this shouldn't pose a problem and should arrive with a fully updated BIOS.
For that particular board, you're in the clear. You should obtain a compatible CPU to upgrade it with the BIOS that supports your 5500. The AMD Boot Kit tool is said to still exist but I'm not certain. The best approach is to take it to the store where you purchased it or a nearby one if you bought online, and request a BIOS update. Additionally, note that I don't suggest purchasing a Ryzen 5 5500 unless a Ryzen 5 3600 is available at a similar or lower price on the used or new market. It offers better value and comparable performance since the 5500 removes its L3 cache.
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