Brother, just because one bachan is true, doesn't mean all bachans you hear about are true as well. Some of these are made up or exaggerated. Especially the ones involving Guru ji performing some kind of miracle. If you say you saw the arch sway back and forth, then I believe you. However in my experience, buildings only move during an earthquake.
Say that I claim Guru ji blessed a lake, and I build a gurdwara next to it. Then I state that anyone who takes blessings from this Gurdwara and bathes in that lake will be cured of all illnesses. Do you know how many innocent/foolish/ignorant people I could get to come to that gurdwara? Do you know how much money I could make from the golak? If I opened a lot of these types of gurdwaras, then I could arrange a gurdwara tour service and build hotels to lodge all of these people. I would be rich. That is exactly what is going on. SGPC makes loads of cash off of yatrees who come from far and wide to do matha tekh at the site where Guru Ji Maharaj once told a story, or made water come out of thin air, etc...