5Vsb is required by the ATX spec from the power supply.btw +5vsb is not a thing on a modern platforms the only thing its used for is usb everything is 3.3v or 12v now
However, this doesnt mean a motherboard needs to use it/feed power to the usb ports, etc. What each motherboard does with it is up to the discretion of the board/AIB. Back in the day (like pre 2010), I recall jumpers on some boards enabling or disabling it.The ATX specification requires the power supply to produce three main outputs, +3.3 V, +5 V and +12 V. Low-power −12 V and +5 VSB (standby) supplies are also required.
Edit: I'm not going to split hairs on the word 'normal'... this is simply something that happens with enough frequency that the behavior can be considered normal (for many boards across AIBs and generations - not all). I dont recall specifically if it is Asus ROG High-end boards or what. But, memory training on some boards is normal (and can be annoying). It s happening on my omega across several bios updates and 2 different psus, OSs, stock v. overclocked, etc and I recall this happening on dozens of motherboard reviews over the years.