Maybe too simplified ?
'Shorter' crank length can be an advantage as one pedals at higher cadence - less leg movement makes the process and coordination easier, especially if your muscles are not trained to ride efficiently at higher cadences. Riders who have a wide cadence comfort range are less reliant upon the crankarm lever...
A longer 'lever'/crankarm, at the same gearing, allows a bit more force/torque applied. Since we're talking mm, the relative difference is very small. The leverarm increase, going from a 165mm to 175 crank is lest than 6% - not significantly noticeable at difficult climbing grades. If you are climbing at your max at 6 mph, think what a 6% improvement means...
If you are right at the edge of your power range, a 6% difference is not going to make any difference on a climb, if you're close to blowing up...
Pedaling is NOT just pedaling, recumbent vs upright (standing)....
When climbing a significant amount of 'force'/torque applied is in part your mass under the influence of gravity (if you're standing on the pedals)... If you're climbing recumbent, the force/torgue applied by can be signficantly in the 'Negative' value, relative to the vector of force/torque of mass/gravity...
Climbing, recumbent, is all about leg power applied... no gravity assist...
There's hardly any real climb which I don;t find myself occasionally getting out of the saddle to get the pedals turning better...

Suitable gearing is the 800 lb Gorilla for anyone,, light climber or gear masher...

Since you have adjustable cranks - give it a try... there's nothing like 'experiencing' ... and if you have a power meter on the 'bent', then you'll certainly see if crank length makes a difference.
Ride On
Yuri