Tested the issue on Andriod and Observed that the app is clearly still running.

Steps followed:
(1) Go to https://roadtrip.glitch.me/
(2) Add to homescreen
(3) Open app, turn on volume of device
(4) Press "Start the road trip" button
(5) Wait for app to start speaking
(6) Put app in background by hitting home button
(7) Use phone normally
Observe that background app continues to speak
(8) Use app switcher to return to app
(9) Observed that app is clearly running.

Chrome version:
69.0.3486.0

Andriod device:
Pixel 2, Nexsus 6P

Android OS:
8.1.0

@malteubl: Could you please confirm device and chrome version you are seeing this issue. Please update to latest canary 69.0.3486.0 and let us know if issue persists.

Thanks!

I have new repro steps that reliably reproduce for me (otherwise it is less reliable):

(0) Install Android Auto App on phone https://play.google.com/store/apps/details?id=com.google.android.projection.gearhead&hl=en_US
(1) Go to https://roadtrip.glitch.me/
(2) Add to homescreen
(3) Open app, turn on volume of device
(4) Press "Start the road trip" button
(5) Wait for app to start speaking
(6) Put app in background by hitting home button
(7) Start Android Auto app
Observe that background app continues to speak
(8) Use app switcher to return to app (You need to drag down from the top inside the Android Auto app to see the app drawer)
(9) Observe that app always reloads.

Tested the issue on Andriod and Observed that the app is clearly still running.

Steps followed:
0) Installed Android Auto App on phone https://play.google.com/store/apps/details?id=com.google.android.projection.gearhead&hl=en_US
(1) Go to https://roadtrip.glitch.me/
(2) Add to homescreen
(3) Open app, turn on volume of device
(4) Press "Start the road trip" button
(5) Wait for app to start speaking
(6) Put app in background by hitting home button
(7) Start Android Auto app>>Observe that background app continues to speak
(8) Use app switcher to return to app (You need to drag down from the top inside the Android Auto app to see the app drawer)
(9) Observe that app is clearly still running.

Chrome version:
69.0.3489.0

Andriod device:
Nexsus 6P

Android OS:
8.1.0

@malteubl: Could you please confirm device and chrome version you are seeing this issue. Please update to latest canary 69.0.3489.0 and let us know if issue persists. 
Attached screen-cast for reference. Please let us know if any thing is missed from our end. 

Thanks!

Here is how it looks like on my Pixel 2 https://photos.app.goo.gl/XZGcrpNbttgB7CDE6

This was in Chrome 69.0.3489.0

Please remove the "Restrict-View-Google" label.

Re Restrict-View-Google: done. Filing a bug under an @google.com address always
restricts by default.

Hmm, that's not expected. Does it repro if you don't use Android Auto? I wonder if it's because Android Auto is doing tricky things while trying really hard to keep itself in the foreground. Like it could try and finish activities so even though we're in bg we keep playing until we're launched from recents triggering onNewIntent and we reload the page.

Peter is most knowledgeable about webapk launch modes 

I can only reliably repro with Android Auto.

Here is a bug report that might help
https://drive.google.com/open?id=1JRulmm2yaW_6F0m9ITQrJomgCtjD_iB9 (shared with google.com)