Before/after, I don't see your point. If the small glass fuse were to rupture from an arc, I don't think you can with out a doubt say what the path is.
Let's assume I am full of shit and you and I both agree that this is a 100% safe and controlled method. (I'm not saying that) Ask yourself, why did Fluke stop this practice.
I suspect they helped to shape the safety standards we have today.
Well I agree that there is no before or after unless we're talking about actual lightning or something--the fuses are in series, so the same current must flow through each, at least at first. You aren't going to rupture the small fuse into an ionized plasma with a small current, say 10 amps. However, that 10 amps will blow the big fuse very quickly and open the circuit. The only way I see a problem is if there were a high voltage DC applied with limited current. Say you had a 1kV DC supply limited to 3 amps--you would blow the small fuse but not the big one and now you have a 3kW arc across the little fuse. There probably are other scenarios I haven't thought of.
On my version of your meter, the 8505A, I found two blown fuses and the 39.1K X-Ref input resistors were melted. I've wondered how that could have happened. I looked up those fuses and one thing I noticed is that they are only rated for 170VDC. I replaced them with a a 1kVAC/DC 10kA rated fuse, which I think is better overall protection than 600VAC/170VDC 100kA.
https://www.mouser.com/datasheet/2/643/ds-CP-0ADBX-series-1664157.pdfAs far as why Fluke would discontinue the practice (while apparently some other manufacturers continue it) it probably is just a case of consolidating their designs--all of their meters appear to use the same 0.44A/11A pair of fuses--and eliminating both known corner cases and possible unknowns. IOW, they have a known solution (the particular fuses) so why add parts and expense and increase risks just for a user convenience?