Assuming one satoshi per byte fee rate and 2,000 transactions in the whole block, saving 5 bytes per transaction would mean earning 10k satoshi per block (and leaving some room for 40 more transactions 250 bytes each). Of course it is negligible for big miners, but for smaller ones it may be profitable, if they could fight for some satoshis. And the profitability limit will be quite high, because truncating five or six bytes may be profitable, but hitting eight or more will be exponentially more difficult, so it rather encourage hitting more transactions than more zeroes in single transaction.
10k satoshis are only worth $3.62 currently so I don't think even the smaller miners will benefit from scouting smaller r-value transactions. They will be more focused on getting their blocks broadcasted as quickly as possible because them finding a block is rare, they wouldn't want to waste valuable seconds just to earn a few extra bucks.