I agree. On the /6 and /7 machines I'm familiar with, the chrome push rod tube is pressed into the cylinder. The push rod seal is a large block of synthetic "rubber" which, through the material quality of being "springy", works by pushing against both the tube and the engine case, thereby effecting an oil-tight seal.
As these seals naturally age harden due to heat, soap, UV, etc, their springiness starts to wane. The drift shown is typically a homemade tool that allows the push rod tube to be driven out of the cylinder 1 or 2mm to restore the seal's tight fit with the engine case.
It's a temporary measure, since the real culprit is the hardened push rod tube seal. But I agree... if the engine is running really good... then don't mess with it. Do the rings, seals, and valves all at one time. Much better to 'kill 2 birds with 1 stone.'
The top end job is expensive, but the real BMW parts are worth the price. The wise thing to do is to start stockpiling gaskets and seals over the next few months, so that you don't have the full expense at that future date.