Reading your comment I think that sounds reasonable, ie that the device that has been off-line resyncs, or? After all, is that not how IMAP e-mail works? I have computers that have not been online for days/weeks/months and when turned on again syncs all the mail accounts - which is exactly what I expect them to do, regardless of how long they have been off-line. This is using Thunderbird on multiple computers and K-9 mail on multiple Android devices. It does not matter which device I pick up to check my e-mail on, they are all in sync.
From my perspective, this is how I would also expect DC to work (and Telegram is already working).
After all, if you have multiple devices one or more of them would always be expected to be off-line for any reason, however short or long time, eg turned off intentionally, battery run down, not able to sync because not on WiFi/cell service etc. etc.