Yep. In those days in France .30/06 and .308 Win were classified "Category 1: Military Weapon" and it was simply impossible to buy them.
As to the .300 Mag, I remember it as being considered in those days generally as an "African caliber" too powerful for France, and very expensive to feed.
I am surprised that you do not mention the 7x64 in your reply, it really was dominant in the 1980's and 1990's in France, and I would have expected that dominance to continue, as it is a VERY useful caliber due to its ability to use heavier bullets (the perceived Achilles' heel of the .270 Win).
The .280 Rem: Remington's other market mis-read (beside the 6 mm Rem)
The .280 Rem (.28/06) tried in 1957 to replicate in the US the 7x64 european success, and I am not sure that the .270 Win was too solidly anchored in the market that it could not have worked. After all, the .280 was positioned as being able to fire .30/06 class bullets at .270 Win (.27/06) class velocity. However, Remington introduced the .280 Rem in the Model 740 semi-automatic rifle and the Model 760 pump-action rifle. That put the two calibers in two different markets. And to add insult to injury, Remington also initially offered lower pressure, hence lower velocity, ammo (compared to .270 Win) that would function well in these actions. This was another market mis-read, after the 1955 abortive launch of the .244 Rem. And when Remington introduced the 7 mm Rem Mag in 1962, it killed the .280 Rem, notwithstanding the fact that the 7 mm Rem Mag is nothing but a loud .280 Rem, when the .280 Rem fires ammo loaded at the full 60,000 PSI SAAMI spec. Try as they might to rename the .280 Rem the "7mm Express", as they renamed the .244 Rem the 6 mm Rem, the perception damages were done. As they say, "you never get a second chance to make a first impression", and both 6 mm Rem and .280 Rem retain "also ran" status to this day, never mind that technically both 6 mm Rem and .280 Rem are technically better cartridges than the run-away commercial successes .243 Win and .270 Win.
A few years ago I would have said that the .280 Rem is probably a more versatile safari cartridge than the .270 Win with loads in the 140 gr to 165 gr range, but the advances in bullet technology have really changed the paradigm, and I am not thinking about the .270 150 gr slug here, but about the 130 gr. In particular I find the 130 gr TTSX absolutely deadly, all the way to large, tough PG and although I did consider both 7x64 and .280 Rem for my wife PG rifle, the .270 Win won easily: where do you find 7x64 ammo in the US, and where do you find .280 Rem ammo in Africa? Or even the US !?!?