Tested the issue in Android and able to reproduce the issue. Similar behavior is observed since Chrome #60.0.3072.0

Steps Followed:
1. Launched the Chrome Browser.
2. Navigate to the URL: chip.pl
3. Wait for page to load completely.
4. Tap on Chrome Settings>> Download button
5. Wait for page to download offline content.
6. Navigate to the URL: chip.pl
7. Scroll down.
8. Observe that images are not loaded completely

Chrome versions tested:
60.0.3072.0, 64.0.3282.137(Stable), 66.0.3350.0(Canary)

OS:
Android 7.0.0

Android Devices:
SM-J710F Build/NRD90M

This seems to be a Non-Regression issue as same behavior is seen since M60.  Untriaged for further input's on this issue.

Please navigate to below link for log's and video--
go/chrome-androidlogs/813438

Thanks!

This is effectively a feature request. The offliner today does not simulate the scroll or clicks "Read More" button or anything to that effect. Leaving as Available ot help with potential prioritizartion.

This is more bug - Chrome is showing, that page is downloaded and I'm sure, that user is expecting 100% of page, not 20% or 50%. 

If implemented functionality project didn't have anything about similar situation, it means, that it was/it is incomplete and it's not good, that it wasn't notified earlier (even during internal tests).

I've made few tests and mhtmls created in situation when images were shown or not are very similar - I think, that we're close to have it fully working.