many moons ago I was invited to the assembly factory where they assemble (build) the Grand L's. L2900's/3300's at the time. L3010 was it's successor, which was still in prototype phase when I was there. Mind you this was in roughly 1996 or 1997. Japan. They don't tighten them that tight. The machine (at that time) had a specified torque and was calibrated daily. Japanese don't mess around, they like stuff to be RIGHT. Although, they DO make a mistake once in a while--just not often. The processes of assembly are completely different now and I cant' speak for the newer stuff.
The filter which is heavily built to withstand the charge pressure that it is under when the engine is running and clutch is out, is an aluminum base with an o-ring on it. The filter/base assembly is screwed directly to the case which is cast iron. Anytime you have a ferrous metal attached to a non-ferrous metal, they will stick together and that's exactly what happens in the case of this filter (HST filter). It sticks. The design of the filter + ferrous to nonferrous seizure makes them stick together. I always used an air hammer with a chisel tip that was well-worn. Just a couple hits and it was loose, every time. You're throwing the filter out anyway so don't worry about damaging the filter. Just don't beat up the transmission too badly and you'll be fine. They bust loose quickly this way, once loose you just reach under there and unscrew it, and you'll lose maybe a half to 3/4 quart of fluid.
The hydraulic filters are suction filters, which are fed by gravity. Those filters are usually the ones that will lose a bunch of fluid, but I can't recall any hst filters that exhibited the same fluid loss. Most of the time a few oz to a quart at the most.
when you take it off make sure the threaded adapter doesn't come out with the filter. Only had it happen once in 30 years that I can remember. Not a big deal, just watch for it and if it does, unscrew it from the filter and screw it back into the transmission slotted side out. Lastly, because of the design, using a flat base with an o-ring, it will leak if there is any dirt or debris on the transmission where the o-ring and base seat. Clean around the area very well. I had to make a second run to a customer's house 4 hours (one way) because another tech didn't clean the area and a blade of straw was jammed between the hst filter and transmission causing a leak. L3010HST as I recall.