We are absolutely on the same page. I have done this on Buicks, Bonnevilles and the Vans with the 3800 TPI Vin L.. I have yet to have one leak.. In general the seals you are describing will seep over time... Its the reason I use a little bit of sealer.. The seal should be impervious to oil and have no issues with it..
I have never pulled the lower intake without pulling the upper.. Just makes it easier to get to all the bolts for the lower and at the same time it gives me the excuse to do some smoothing and porting... LOL