Normalization/plotting of funcs returned by RooAbsReal::asTF

Dear experts,

I am having problems understanding the normalization of TF1 objects that I get via RooAbsReal::asTF from a multi-dimensional PDF. Please find attached a small macro that I used to produce the following results (with ROOT v5.32, RooFit v3.50):

The first three plots look as I expected them as well as the printout that I got:

Full integral: 1.00013
Quarter of it: 0.250033

However, the plot in the lower right corner looks like the normalization of the 2-dimensional TF1 was off by a factor of almost 8! Is this expected? Or just a (numerical) problem in the plotting? Or am I missing something?

Thanks a lot in advance!
RooAbsRealAsTF.C (1.25 KB)