You certainly can use the spring loaded pushrods on steel rollers. Just remember to plug off the oil feed hole from the rockers with a rivet. Joey you are correct in saying that the spring loaded pushrods are the same length when they are compressed as the 417 pushrods.
I have seen a non engine brake ETech with spring loaded pushrods on the intake side as well. I am not sure if it was factory installed or it was installed by another dealer. It came in because the cam was wiped out.
Joey its not your fault. Installing ceramic lifters takes extra time and care and I am sure with your experience you know and have done them plenty of times.
I used a magnet and placed the lifter onto the cam using a long screwdriver. Also I was very careful installing the pushrods, also I put oil on the end of the pushrod and feel the surface tension of the lifter and pushrod.
So many things could have happened, such as, when the rockers are installed and if they are not installed correctly, when torquing the top end, if the pushrod(s) are not installed correctly, and when the engine is turned you will hear a "SNAP". If it has a ceramic lifter, well then its toast. I was never a fan of these ceramic lifters simply because it does not take much for them to get damaged. Just my 2 cents.
V