175mm or 170mm I've never had a problem shortening a 175 or 170 by 22mm. (Not so far anyway, but it certainly could happen.)
Recently I shortened an orphan 175 to 150 as an experiment, without hitting the tunnel.

165mm or 172.5mm
165s seem to be made from the same forging as 170s.
172.5s seem to be made from the same forging as 175s.
This makes tapping into the tunnel more likely. So, I have modified my tooling to allow me to shorten 172.5s and 165s by 21mm instead of 22mm, to lessen the likelyhood of tapping into the tunnel. However, it is still more likely than the other sizes.

It adds setup time to shorten by any amount other than 22mm, and it took most of a day to modify the tooling to allow it. So, I charge an extra $5 to shorten these lengths. $55 if you send bare arms, $60 if they have the rings and one key extractors.

Out of 3 sets of 172.5 I did tap into the tunnel on 1 arm at 150.5. Since then, I've done 6 or 7 sets at 151.5 without tapping into the tunnel.
On one 165 shortened to 143, I saw a tiny black line at the tip of a thread that may have been the tip of the tunnel. On another one shortened to 144mm, I clearly hit the end of the tunnel with the tip of one thread. I've done about 4 sets to 143 and 5 to 144.

Based on this "Too small to be statistically valid" sample, I'll leave it up to you to decide if it's worth taking the chance.

If I tap into a tunnel, because it is unusually long on your arms, I don't charge enough to be responsible for replacement.
Given that the typical failure mode for pedal eyes is on the sides, and that the pedal will close the slit, it seems unlikely that any failures will occur due to this. The metal there is thick, while it's amazingly thin further down the arm.

I will NOT shorten Shimano 105 FC-5503 or FC-5500    See photo at top for Model # Location on back of crankarm.
These are a cheaper, Non-HollowTech variety that are narrower and therefore do not have sufficient metal in the area where a new eye would go.

Hollowtech MTB cranks
Someone tried shortening a Hollowtech MTB crankset and cut a big hole into the tunnel.
The 105s and Ultegras are old technology. The fact that they can be shortened indicates that they weren't taking full advantage of the idea.

Hollowtech II two piece cranks
Highly unlikely that there is room between the end of the tunnel and the existing pedal eye. Just to find out for sure, my tooling would have to be redesigned and I'd likely trash a very expensive crank.