Some bikes have totally horizontal top tubes, and that puts a hurt on stand over clearance. This is compounded by the fact that horizontal top tube bikes have short head tubes, which puts the handlebars on the lower side. You gotta go big on these bikes to get the bars up. For those bikes, you can cut that 1” of clearance down to 0”, but no less. That’s because you’re always wearing shoes, and PBH measurements are taken without shoes. So if your PBH is 80cm and the bike in question has a standover height of 80cm, you could ride it because shoes add height, at least a centimeter, and one rarely stands over their bike while holding it straight up. When at a stand still, you tilt your bike a bit or keep one foot on a pedal and really tilt your bike. In that last case, standover barely matters at all.
Look at old touring and race bikes. Not even a fist-full of seatpost showing. What’s that mean? Those bikes HAD to be tilted over to stand over. For that style of riding, where you aren’t off and on the pedals much, that’s okay. Now, I’m not advocating for an overtly huge bike, but a properly sized horizontal top tube roadish bike will have minimal standover clearance. It’s not a big thing. Stop thinking about it.
You want to get on the biggest roadish bike you can, because as a general rule, comfortable riding = high handlebars. The bigger the bike, the longer the headtube, which means a 54 cm frame has a 2cm higher (almost an inch) handlebar than a 52 cm frame, right outta the gate. It’s a myth that taller bikes are longer, and that you should fit to the top tube length, not the standover.
Let’s look quickly at some geometry numbers to investigate this further. On the surface, a Gunnar Grand Tour 52cm has a 54cm top tube, and with a 100mm stem with 25 degrees of rise, with 4 inches of spacers under, it that bike has a handlebar reach (called the Handlebar X measurement) from the center of the bottom bracket to the center of the bars of 40cm. The Handlebar stack, called the Y measurement, is 75.6cm.
A 54cm Gunnar Grand Tour has a top tube 1cm longer, at 55cm. With the same stem and spacers, the Handlebar X is…. 40cm. No more reach! The bars are higher, and as bars get higher, they get closer to you.
A 56cm Grand Tour has a top tube that’s 56cm. The Handlebar X, with the same stem and spacers is…. 40.2 cm. But the handle bars more than 3cm higher on the 56! It’s easy to make bars low. It’s hard to make them high enough to be comfortable. Bigger frames allow you to bring the bars up with very minimal reach consequences.