Is it ok to have an 100% of one coin as a portfolio ?

Whilst I understand my title confuses itself with one coin making up an entire portfolio , but for periods of time I've held just one coin with my investment funds .

And whilst I understand one coin might drop one day and you don't have a supporting coin to help keep the portfolio up , I'd argue that aslong as it's what you would argue as a relatively top 10 secure coin, and not some shit coin pump and dump , it's understandable to have a 100% of one coin as your portfolio , if you're in it for the long run and believe in the project itself , it shouldn't be too much of an issue ?

Edit - my argument for example would be holding 100% ETH OR BTC , or even BNB?