In your scheme you can't tell the difference between the single byte binary input 0x01, and the four byte binary input 0x00,0x00,0x00,0x01.
Those are the same if you're treating the binary data as a stream of 32 bit numbers, but not if it's a stream of an arbitrary number of octets.
Your parent is suggesting that if after chunking the input into 5s, your last chunk is "10" you would treat that as 0x01, "100" as 0x00,0x01, "1000" as 0x00,0x00,0x01 and only "10000" as 0x00,0x00,0x00,0x01. That's not four encodings of the same value at all.
Treating "1" (or any single leftover character) as invalid in such a scheme makes sense because a single character can only encode 85 values, from 0x00 to 0x54.
Those are the same if you're treating the binary data as a stream of 32 bit numbers, but not if it's a stream of an arbitrary number of octets.
Your parent is suggesting that if after chunking the input into 5s, your last chunk is "10" you would treat that as 0x01, "100" as 0x00,0x01, "1000" as 0x00,0x00,0x01 and only "10000" as 0x00,0x00,0x00,0x01. That's not four encodings of the same value at all.
Treating "1" (or any single leftover character) as invalid in such a scheme makes sense because a single character can only encode 85 values, from 0x00 to 0x54.