I should let you talk to a customer of mine that brought in his custom tandem for a few modifications and I had to call him back an tell him his tandem was trash due to the fact the 1/4 vent holes in the BBs were plugged and caused the internal corrosion that killed his tandem. Dozens of black pin holes through the paint in all the lower tubes.
Holes should be as I stated before at each end of all the tubes. Regardless of lugged lugless construction if you want the frame to last. Of which the most critical is a hole or cutout in the BB shell.
Due to my predecessors I have extensive experience with internal corrosion. This is one aspect of the industry where it has failed both in the production and custom parts of our industry. If the frame is only ridden in “nice” weather then it will not be an issue. If it is a work horse or will be ridden often and in all conditions then precautions must be taken. You only have to step out of this industry and look at others to see my point. That is were I will end it.