OTOH, do you expect every new LIR to ask for a /28?  I admit I have not
read the proposal yet, but if it's in line with what we currently have,
a LIR could just signal "a /32 is good for me" and get one of those /29
holes...

To give some numbers on this:
Of the 628 allocations that have been done to LIRs in 2024 so far we have 560 /29 and only 68 /32. So the vast majority of LIRs (about 90%) have opted for /29 allocations, with only a small fraction choosing /32 allocations. 

If given the choice between /28 or /32, it's likely we would see a similar trend, with the majority of LIRs preferring the larger /28 block for future scalability and flexibility, similar to the pattern observed with the /29 allocations.

(Data from delegated-ripencc-extended-20241017 file from the RIPE ftp server.)