I agree with you that the cumulative update could reach a stage that it cannot be managed by excel. In that case, you can copy the update from the pivot table (which cummulate the data from different week), and past it instead of all the weeks data. This will reduce the volume of the data and you can repeat this step whenever required.
Regarding getting the update from the site team, it depends on the project natural and construction team background. In some projects i used to receive the updates in PDF file, other projects updates were in excel. At the end of the day, we are just telling you what we believe it is the best solution, you can modify, add, and omit to develop your own system to best fit your project.
I hope my reply answered your questions. If you have any further questions, please feel free to ask, but be specific.
Best Regards,
Hany Ismael