The scale of work would be a lot, lot, lot smaller if they had made native apps to start, and could use the built in accessibility stuff instead of having to reinvent the wheel.
Is there a reason Electron apps can't take advantage of the accessibility features built into Chromium? Having separate platform apps runs into the issue of the user settings page being accessible in the Windows app, but unusable with a screen-reader in the Mac app because of a bug, etc etc.