Let's just say that +Thuc "simulated" the consecration in 1981...then it's invalid.
But where is the proof that his OTHER consecrations are invalid? Each individual consecration/ordination is judged independently.
Well glad to have got you to move out of the echo chamber brain rot for just a minute (Laddy is another story)
So to answer your question, yes and no. If he was still alive, he could be interrogated more rigorously as to whether the withholding intention was down to mental incapacity or just malice.
Ironically, if it was just malice, it would weigh more in his favor, as it would show it was more targeted against that group. There are indeed, I'm not going to lie, some signs which give strength to that argument. Simulating a Sacrament is still a very, very grave sin by a member of the clergy, and public repentance would be required, but that's not to do with validity. However it could be to do with validity if there was at least one other instance of him doing it. That would certainly erode trust and cast doubt in that way.
Now if it turns out he was mentally ill and this was the reason for withholding, then that's a whole other ball game. Because then a mans entire reason is called in question, and therefore the veracity of ANYTHING he says. Since it concerns important things, we can no longer make the assumption of right general intention. What if he made the broad general intention at some point that all his Sacraments from now on would be simulated? Or did it once off in another instance, but this time NEVER revealed it? We have to ask those questions, and deserve answers. But we can't get them now.
On the flip side of this you might say his mental illness excused him in one instance, and that we can argue general right intention overall. This would be also a valid argument.
But you see now, I hope, how we just can't speculate on this. We need to talk to the man himself. There are too many variables to know for certain. A policeman, or judge would never carry on with such limited information and neither should we.
In Church terms, a negative doubt would be saying "its invalid because he looked the wrong way! and said he didnt like the priest". Of course we should presume validity in that case. A positive doubt however is totally different, whether it concerns the rites themselves or the intention.
The whole thing turns around when the minister says he withheld intention. Because coupled with mental illness and instability we are not acting on certain ground anymore. If he was alive we could get back onto certain ground. But we just don't know now if he did the same for the other Sacraments. We can't just "take his word for it" anymore like we would a normal Bishop, that's the problem.
There is a deep, deep uneasiness there that can only be resolved by conditional ordination and consecration.