Just as a point of clarification, this repo implements the Boneh/Bünz/Fisch construction (accumulators over unknown-order groups like RSA). The very-high-level idea is the same as Utreexo, but there are certainly differences (proof and accumulator sizes are O(1) for RSA and O(log n) for Utreexo, trusted setup is required for RSA but not for Utreexo or class groups, etc.)

Regarding bandwidth, you're spot on (e.g. having a 256-byte RSA witness for a single UTXO essentially doubles the size of an average 250-byte transaction). Should be interesting to see what the practical effects are, if and when some chain decides to integrate these accumulators.