FT817 output power on battery supply: 5W or not?

There is a common misbelief that the FT817/FT817ND transceiver does not output 5W when powered with the internal 9.6V battery pack, or with an external source lower than 11V. The user's manual doesn't say that, at least the English language version.

So, does the Yaesu FT817/FT817ND output 5 Watts when powered with the internal battery pack? Does it output 5W when the "LiiI" icon is flashing?

I did the measurements and posted a video on youtube.

The setup includes a 26-30 MHz wattmeter (10W f.s.) and a dummy load, stock 1400 mAh internal battery.

I measured the output power at 5W and 2.5W level with the internal battery and external PSU. The sequence in the video is battery, external and then battery again.

The result? Even if the icon is flashing, the radio is capable of outputting 5W.