When it is infrequent sexual innuendo that only occurs every so often in conversation, it isn’t a red flag.
He is a guy that you matched with on a dating site.
To this end, he has a physical attraction towards you.
He likes what you look like, and as a guy, he expresses his physical attraction towards you with occasional sexual innuendo in conversation.
As long as these sexual innuendos aren’t crude and disrespectful, it isn’t an early red flag that he brings in sexual innuendo from time to time in conversation.