Then WFA came out and all of the sudden people's expectations of what is a good repair speed went through the roof.
Actually, from what I remember, people noticed SPios repair speed quite quickly and complained that its too fast.
Back then it made sense, with the resource penalties and limited armor, you had less tanks so you needed to get them back faster to combat, but a LOT has changed since.
USF, well USF is kind of balanced in the repair speed, sure they have the crews, but they won't repair the tanks in 5 seconds, pretty much the only difference between USF and vanila is vehicle crew basic engi independency, repair speeds themselves are ok.
Brits as I've said, pay hefty upgrade costs and lock down awesome tank to repair fast.
And we have OKW, being the special snowflake as ever.
Tuning down spios rep speed is also a valid option right now, though I'd still do something to help pios and CEs get to vet2 more reliably.