"A different environment and challenges have been great for my rugby."
Horwill has played 21 games and poured 1527 minutes into his Quins season, more than double the playing time of former Test lock partner Rob Simmons at the Reds this season.
Michael Cheika may have overlooked Horwill for last year's World Cup but the pair still caught up for coffee on the Wallaby coach's recent visit to Europe.
"We had a good chat and when Cheik said 'would ya?' I gave him a pretty quick 'yes' to being available to play for the Wallabies again if needed," the 61-Test Horwill said.
Rubbing shoulders with Robshaw, Joe Marlar, Danny Care, Mike Brown and England's new backrow bench weapon Jack Clifford at Quins has given Horwill a good grasp of Jones' impact.
"From what I've seen, Eddie has just given the England players a lot of belief and resurrected them from a poor World Cup with good structures around the team," Horwill said.
"A guy like Robshaw unfairly copped it as the fall guy for England's poor World Cup but Eddie has given him a lot of confidence.
"They'll head to Australia as a different beast and be a genuine threat in all three Tests but it's still 3-0 to the Wallabies.
"I cop stick about the Aussie cricketers in the Ashes from the Quins boys and my easy comeback is always their home World Cup."
Horwill added an extra twist to speculation that strong-running No.8 Leroy Houston may be on the move from English club Bath to his old home at the Reds.
"Bath have just signed Welsh No.8 Toby Faletau and have an all-internationals backrow so it will be interesting to see what that means for Leroy's plans," Horwill said.
At Ballymore, fullback Karmichael Hunt (groin) and reserve hooker Saia Faingaa (foot) both sat out Reds training ahead of Saturday night's clash against the Hurricanes in Wellington.