Suggestions are given. What you do or do not do is your decision.
It is good to know the large online update was a success. There are users who have been updating TNAP 7 for months without ever flashing the image. I can only wonder how their receiver is running as compared to a receiver that was updated by Image Flash.
For normal maintenance, an online update is convenient and usually OK. The recent image changes are not normal maintenance.
In some instances or situations, packages that are new may be missed by an online update. This is WHY the suggestion to flash was made. The command `opkg upgrade` primarily knows:
1. Which packages are currently installed.
2. Which newer versions are available in the feeds.
3. Which dependencies those packages require.
`opkg upgrade` does not automatically compare the receiver against the complete package manifest of the newest image. A freshly flashed image, however, is built directly from that current manifest.
Over time, continuously online upgraded systems can accumulate:
obsolete packages
unused files
old configuration(s)
remnants of previous image designs
A fresh flash removes much of that historical baggage and may provide a better user experience.