Crosses were reused, and at that time often where not true crosses at all, but merely crosspieces nailed to old olive trees
So9
Wood was in short supply, and crosses were reused.
Helena miss labeled Mt. Sinai, she was a body of water short...
Which would go a long way in explaning why the word "tree", rather than "cross" is used in Acts 5:30; 10:39; 13:29; Gal 3:13 and 1 Peter 2:24
I would go a bit further and say that the two robbers were nailed to the same tree as Christ. Since Christ was between the two theives, but they came to Him last. If He was between them, wouldn't they come to Him second? unless they were on the same tree.
Being that the centurion saw the temple veil split in two, clearly they were at alititude (to see over the wall) and directly east of the temple. This points to the southern slope of the Mt Olives; which is the same site that Abraham and Isaac went.