Yeah, these options have been there
for years and have not changed in a number of years.
Home -> Settings -> About Phone -> Software Updates -> 'Update over Wifi Only' ('Auto-download system updates' , 'Auto-update apps')
On Sprint and T-Mobile you can choose to turn off Auto-download system updates and Auto-update Apps. With Verizon, It looks like the only option is to force the update to download over wifi. If you only use wifi, your download probably would just start itself, shamefully. There should still be a hard stop before the install takes place, a check box to confirm you want to install the recently downloaded file should come up (Install Now and OK should have to be confirmed). But maybe Verizon took that out too?
http://www.htc.com/us/support/htc-10-sprint/howto/744904.html
http://www.htc.com/us/support/htc-10-t-mobile/howto/739573.html
http://www.htc.com/us/support/htc-10-verizon/howto/744622.html