Willie did see Efren play - at Hard Times in around 1990-91 we put on the Willie Mosconi Open and Willie made an appearance there and even did a couple of short exhibitions. I had to remind him if he was shooting a shot for the second time because he had some memory lapses by then.
Efren played in that event (9-Ball) and Willie watched part of one match. I sat next to him and gave him some background on Efren. Willie sat in silence for a few minutes and then said, "He has a nice game." He made no comment on his stroke or stance or anything else.
We also did a one hour long interview that was recorded on video where Willie discussed his life in Pool. Unfortunately and unbelievably, the guy who recorded it accidentally erased it as well. He asked me to do it again and I refused. It was enough to put Willie through all that once and I wasn't about to ask him to sit through it again. That experience was a tremendous disappointment to me as we had some classic stuff on that tape.