Accepting BTC is a newsworthy event, and you can lessen the impact for conservative stockholders by implying 100% conversion to fiat: "At this point bitpay converts all paid BTC to USD at the moment of sale so there is no exchange risk". However, CHANGING that 100% to 90% then 50% then 0% is easy and can be done without any external difference.
WRT the idea that merchant adoption = short term slide, places like coinbase make it so easy to cash out that this seems unlikely.
The citi report mentioned that if a company does hold some amount of fiat then their overall risk profile would be worse. Also if a company does not have any expenses in terms of bitcoin then they would have nothing they can use their bitcoin for.
Most companies are not in the business of speculating.