Just ran the upgrade wizard
New Installation makes comment about 8Gb required but doesn't say incompatible.
What is the starting point
Even if start at SecurePlatform and Gaia R80.40 as endpoint then says need to do an R80.30 intermediate.
Maybe updated since your customer ran however certainly not seeing what you have had reported to you.
Would run it yourself and see what you get, certainly get the customer to run again but I certainly wouldn't say that your statement is correct based on what seeing.