having found this thread on discovering that I too was suffering with the same auto substitution issue in the location field of Calendar...
I tried the suggestions here but nothing stuck 100%, so I called Apple Support (I've got AppleCare, so might as well use it)
Explained to a Level 1, then a Level 2 tec and he took the problem away and sent me a very prompt response the following day.
Here is the important bit of the response:
"Engineering have confirmed that they have received reports worldwide regarding the issue of location lookups/ autofill and the fact that they are shortening addresses and not allowing the customer to choose a suggestion as averse to have one forced upon them.
They advised that at present the issue is just beginning to come to light likely due to recent updates etc and they are currently investigating these reports.
They confirmed that they have al the information they need at this time and agreed that any solution is likely to come via another software update however they were unable to speculate on the expected turn around time at this point."
...please don't shoot the messenger 😉
but it pays to make that call or press that feedback button....and of course post here!
The only 100% workaround is to paste the address, the way you want it, in the Notes field until the permanent fix comes for the Location field.