Hello @Managor, Steam's shader pre-cache is incrementally updated as shaders are seen in the wild with each game. There's a relatively small subset that get updated in any given shader pre-cache incremental update.
In most cases, there shouldn't be a significant effect from the late non-essential update cycle you've described since the most commonly used shaders should already be in the slightly older shader pre-cache data set. I have to disagree that this should block the start of the game.
Let's use this issue report as a feature request for this behavior to be tunable.
There is one related issue that I noticed that's related when it comes to Apex. Because the shader patching hogs the hard drive, the game can't load the shaders it needs . For some reason the loading stops at around 5k shaders in the main menu and then never proceeds past that
Nothing extracted yet.
Your system information
Steam client version (build number or date):

Distribution (e.g. Ubuntu): Arch Linux
Opted into Steam client beta?: Yes
Have you checked for system updates?: Yes
Please describe your issue in as much detail as possible:
When a games is set to "Only update this game when I launch it", Steam will start downloading shader caches for that game only after the game has launched. I want to set this for Apex Legends because I don't want to patch 10GB of shaders every day when I launch my PC.
Steps for reproducing this issue:
The launch window should wait for the shaders to download but instead the game launches and leaves the shaders downloading in the background which doesn't help.