Hopefully this will help clarify things a little bit.
The two holes in the front main bearing cap are the drain holes back to the sump. The rear main bearing cap has two just like it, only a bit bigger. Oil is pressure fed to the front main bearing and to the front cam bearing and on up to the rocker assembly. As the oil film drains off the bearings, it collects in the bottom of the timing cover and drains back to the sump. The timing chain passes through the pooled oil and lubricates the chain and both cam gears. The slinger/shield helps direct oil onto the chain and keeps too much oil from the back side of the seal. Don't gob on the silicone when putting the timing chain cover gasket on. Excess silicone can clog up the holes and prevent drain back to the sump.
I like to use a little assembly lubricant on the chain and the gears when building the engine. Put this on with a small brush just before the cover goes on. Helps give the chain and gears some lubrication before the engine's oil pressure gets up and oils the assembly per design.
The hole in the picture, about halfway up the block is a vent hole and could act as an overflow relief if the two drain holes are clogged. The front timing cover is vented on the 1275 and that is the primary path for the crankcase ventilation. If you are rebuilding the 1275 in the top picture, take a grinding stone and clean up the casting flash blocking part of the hole. Round the edges to eliminate stress risers. Be sure to clean the block with plenty of hot water, soap and then blow dry. Spray the bores/machined surfaces with WD-40 type lubricant for water displacement before blowing dry.
Also, in the top picture, the lower bolt holding the front plate on is a hex-head bolt. Be sure to use the counter sunk bolts as shown in the second picture. Otherwise, there could be interference with a double row timing chain.
Take care and hope this helps with your original question.
Mike Miller