UserAgent: Mozilla/5.0 (X11; CrOS x86_64 11021.81.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.110 Safari/537.36
Platform: 11021.81.0 (Official Build) stable-channel eve

Steps to reproduce the problem:
1. Open a web app with a drag-able UI element not optimized for touch (see sample list of affected UI elements below)
2. Put Chrome OS device into tablet / touch-only mode
3. Attempt to drag the UI element by touching and dragging on the screen

Sample drag-able UI elements that do not work, for step 1:
A:
* Open keep.google.com or the associated web app installed from the Chrome Web Store
* Using keyboard and mouse, create a new checklist
* Add several items to the checklist
* Drag-able element: click or tap on a list item, causing the six-dot grab handle to display to the left of the element text
  - dragging rightward on the handle with a mouse will indent the list item
  - dragging up or down on the handle will change the order of the list items

B:
* Open photos.google.com or the associated installed web app
* Select several photos (via mouse: hover over photos and click the checkmark in the top left) and use the "+" icon to create a new album
* Open the album
* Click the triple-dot icon in the top right and click "edit album"
* Drag-able element: using the mouse, you can rearrange the photos in the album by clicking and dragging them around the page

C:
* Open calendar.google.com
* Create a new calendar event
* Select the "week" view view the top right drop-down
* Drag-able element: click and drag on the calendar event to move it to a different day/time

D:
* Open drive.google.com
* Create a document in the drive's root directory (i.e., so it appears in the file list shown when opening drive.google.com)
* Drag-able element: click on the document an drag to the left to drop it into one of the folders within your drive

etc.

What is the expected behavior?
The UI element responds, as if one had clicked and dragged on the element using a mouse

What went wrong?
The UI element does not respond. Putting your finger down on the element and immediately moving it around is interpreted as a page-wide scrolling event. Putting your finger down and holding it in place for a second before moving it around brings up a context menu, as if one had right-clicked with a mouse.

Did this work before? No 

Chrome version: 70.0.3538.110  Channel: stable
OS Version: 11021.81.0
Flash Version: 31.0.0.148 

As to why this should be considered:

At a technical level, it could be tempting to say "There are different APIs for handling mouse events and touch events in web pages. This is WAI -- web app developers should update their designs."

However:
1. At the risk of stating the obvious, end users do not care why something does not work. They care that it does not work. Devices sold as tablets with desktop-class browsers, it can reasonably be argued, should be able to touch-interact with desktop-class web apps.
2. Developers, of current and legacy applications, cannot be assumed to be using the latest and greatest web APIs
3. Even major, first-party Google web apps that come pre-installed on many Chrome OS devices, including some of the examples listed in "steps to reproduce" above, do not have touch-friendly implementations of drag and drop, let alone third-party apps.

Another possible response: "if you want touch, use the associated Android apps."

However:
1. The Android apps are often less feature-complete than the associated web apps
2. As indicated by what is pre-installed on new PixelBooks, the web apps are considered the "preferred" versions under Chrome OS for several of these services
3. Certain Chrome-OS-with-touch features are exclusively available in the web app versions; e.g., low latency pen input with touch event rejection for pen note-taking in Keep

In the interim, it may be useful to forward these examples to the respective teams internally; for my part, "knocking on the front door" via external "send feedback" reports has a way of proceeding slowly 😉