Chevy mystery on cam change

I am in the process of changing out my camshaft as discussed on a couple of threads on this site. Before I opened anything, I placed the engine at the #1 TDC on the crank and verified this with the distributor rotor pointing at the #1 spark plug wire. When I opened the timing chain cover, to my SURPRISE the timing marks were NOT facing each other. The cam mark was at 12 clock and the crank was at 12 clock. Every time I have changed gears and chain, the instructions always state to move the engine so that the cam is at the 6 clock position and the crank is at 12. Is this just for ease of installation and the engine is ACTUALLY at the #6 TDC?
If this is true, there aught to be WARNING LABELS!!!
This would explain numerous builds where I had to rotate the distributor 180 to get it to run. I was so embarrassed.
If this is NOT true, I am in serious trouble. The engine ran fine for 36,000 mile like this AND I changed out the cam and put it back just like I found it. Both cam and crank at 12 clock. Do I need a tear down?
I am only writing this thread for clarification to all of us casual gear heads.

Dot to dot ,cam at 6 crank at 12. This puts ,....no 6 I think at tdc.
Cam at 12 and crank at 12 puts the no 1 at tdc.

thanks shawnlee
I got it running
I had to do a cam break in so when it fired I ran it
missed the dist gear one tooth so it was really retarded but I got the run in
Properly timed, it runs fine thanks for the reply
I repeat; "When changing cam gears and timing chain"
Dot to dot, cam at 6 crank at 12. This puts the engine at no 6 at tdc.
Cam at 12 and crank at 12 puts the no 1 at tdc.
I learned something new today!
I think I will get cleaned up and enjoy some cold beverages.

Manufacturers following GM's guidelines "assumed" or filled out the contract with the attitude that the running engine with nothing being changed ( such as broke down on the side of the road or no distributor removal, etc), well, it doesn't matter. I have spent many years wondering why (not too intensely), but it doesn't matter since the answer has been given and viewers know that it has been corrected. Good job Shawn, you got him going.

That Right Dot to dot #6 is at TDC and #1 at over lap.