No, it is completely normal, it been like this since Windows XP, Vista, 7 and 8 on my old laptops.
You probably have a faulty battery or maybe have incompatible battery driver installed. Your tablet should never install updates when battery is low at 20% or less and battery saver mode should activate automatically which will suspend windows update and downloading updates will resume if you plug in outlet to recharging battery.
A few months ago at one time when my Surface Pro 6 battery was low at 20%, battery saver was activated and suspend windows update then at 10% I decided to deactivated battery saver and resumed windows update automatically installed few updates, shutdown and took a few seconds to reconfiguring updates to 30% and restarted few seconds later to another reconfiguring updates to 100% lasted a few seconds and logged in just to see battery reached 8%.
2% is good enough to completed updates.
People like you really need common sense when battery is low so you will need to RECHARGE the battery. Many people had done similar mistakes when updated their Android phones and iPhones with security update or firmware update when battery is low can cause Android and iPhone fail to unbootable, they will need to perform firmware recovery to restore their phones to get it boot up again by recharge battery FULLY!
It happened to me once with my old Galaxy S3 when battery was at around 40%, I thought 40% would be good enough to do security update but the update process was failed and caused Galaxy S3 to unbootable, thankfully firmware recovery restored my phone by recharged my phone FULLY! I will never update my phone again when battery is low so will always update when phone is FULLY recharged.