Installing 3.5" LFF backplane ( 743020-001 779083-001) into ML 350 Gen 9

[Int-Circuit]

Hi everyone, I'm in the process of buying a HP ML 350 gen 9 tower server.
This one has SFF bays, which kinda bugs me as 2.5" high capacity hdd are more expansive than their larger version.
After browsing on r/homelab, I read about the fact that the ML series can have additional drive cages added to expand the storage. This got me thinking about what could limit you to mix and match sff and lff backplanes as those would use the same power and data connectors.
After asking Serverschmiede on eBay about that, this was their response

Hello,We did not try this yet, but in theory it should not be a problem to mix LFF and SFF.
You will require those parts:
1x Bitte entschuldigen Sie die Störung...
2x Bitte entschuldigen Sie die Störung...
1x HP ML350 Gen9 8x LFF SAS SATA backplane 743020-001 779083-001 (The backplane is currently not available, but you can use the part numbers to find it.)
Best regards

The question I have is: Is it possible? Or is my reasoning flawed?

Thanks a lot in advance
Int-Circuit