Uh no.
That photo first appeared in this post
https://www.tractorbynet.com/forums/yanmar/201072-getting-my-ym169d-fixed-up.html#post2327897
It shows a YM186D that has PowerShift, and the orange lever on the left is the shift lever.
YM169D has a 3 speed manual transmission. (Both those tractors also have a range selector sending different gearing into these transmissions).
This old thread
https://www.tractorbynet.com/forums/yanmar/170137-mowing-big-twin-ym240-vs.html
shows where I stalled mowing upill with the YM186D in tall grass and 4 ft mower. That mower loads that tractor so hard that it feels like it is working hard under most conditions. And its powershift helps a lot, I often gear down while moving if the going gets difficult. A manual transmission can't do that, it would have to start from a standstill spinning up the stalled mower and turning the wheels at the same time, to get moving. This was sometimes difficult with the YM240, YM169D would be worse.
In conclusion a 4 ft mower will work that tractor hard but its manageable in short grass. Tall stuff will need small passes, maybe 1/3 the width of the mower.