Is this just the difference between Mac and PC

Hello
I tend to waffle so I will try and get to the point
on a Macbook pro
-I used Makerlab app- Image to 3D.
-I exported it from Makerlab and it defaults to saving it to my Downloads folder.
-Firstly it saved as a zip file (result.zip) and I unzipped it to have a folder also called “Result” that contains two files , source.mtl and source.obj
-right clicked on the source.obj and selected open in bambu studio.
everything went well
-Then copied the zip file to a destination in my documents folder, unzipped the file and with both files showing once again right clicked on the source.obj file and selected open with Bambu studio only to be paused by this message.“load mtl in obj: failed to parse”.

It seemed that buy moving the zip file It some how corrupted itself. I then tried to move just the .mtl file and the .obj file with the same results.

my next brainstorm was to email myself the two files that I had unzipped and moved into my documents folder .
-opened the email on a PC laptop
-downloaded the attachments from the email , source.mtl and source.obj
right clicked on the source.obj and selected open in Bambu Studio and everything worked like a charm.
-as another test I deleted the newly saved from email files and once again opened the email and only saved the source.obj file to my download folder and again tried to open it and this also was successful.
-Once again moved just the source.obj file to a new documents folder and this also was able to open in Bambustudio

My question is
Is this a mac versus PC thing or have I messed a step
I would like to use the mac but I cannot continue to leave the working files in a download folder when I would like to organize all of my projects in their dedicated folders.
Sorry for the length but I wanted to explain as thoroughly as possible
regards
Tony