Correct. On blackface amps, the spring reverb circuit is located between the 2nd gain stage of the Vibrato channel and the phase inverter. This is not possible in the Axe FX since we can't place effects between the preamp and power amp. You have to pick either in front of the amp block or after. In front, it will have more compression and color from the amp, better for wetter, surf style reverb, but if you push the amp into breakup, the reverb will breakup too and can get muddy when driven hard. Behind the amp block it will be a bit more "hi fi" sounding and clear. In front of the amp block is probably more authentic sounding since the preamp of non-master volume Fenders runs quite clean and you'd get the same compression and breakup on the reverb in the power amp section when the amp is pushed hard. The reverb knob on the amp controls how much of the wet reverb signal gets mixed in with the dry signal from the Vibrato channel, so the MIX control in the reverb block would accomplish basically the same thing. You'll typically need lower MIX settings with the reverb in front of the amp due to the compression from the amp.
One exception is the Vibro King. It actually has a version of the standalone tube reverb unit built in at the very input of the amp, so for that amp, the correct place is in front of the amp block.
No Fender amps prior to the Vibroverb in '63 had build in reverb. Earlier amps like the tweeds, blondes/brownfaces would have used a standalone reverb unit in front of the amp or they would have added external reverb at the console with a studio plate, spring, or real reverb chamber.
Also, when combining spring reverb and tremolo, make sure you put the tremolo after the spring reverb so the reverb tails get tremolo as well. Blackface Fenders had the tremolo dip the signal just before the phase inverter, except the Princeton Reverb which still used bias reverb in the power amp section.